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 Subjects -> CHEMISTRY (Total: 871 journals)     - ANALYTICAL CHEMISTRY (54 journals)    - CHEMISTRY (610 journals)    - CRYSTALLOGRAPHY (21 journals)    - ELECTROCHEMISTRY (26 journals)    - INORGANIC CHEMISTRY (42 journals)    - ORGANIC CHEMISTRY (48 journals)    - PHYSICAL CHEMISTRY (70 journals) CHEMISTRY (610 journals)                  1 2 3 4 | Last

1 2 3 4 | Last

• Obtaining and Characterizing Nylon 6.12-Pseudoboehmite Nanocomposites -
Mechanic Tests
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Antônio Hortêncio Munhoz Jr., Alber Luiz do Nascimento, Cesar Denuzzo, Gabriel Cavalcante Gomes, Leila Figueiredo de Miranda, Maura Vincenza Rossi
Polymer nanocomposites are formed by nanometrical particles embedded in a matrix. Additions of small amounts of nanoparticles of inorganic material in polymer matrixes can greatly improve mechanical properties when compared with the pure polymer. The high specific surface area of the inorganic nanoparticle materials promotes its dispersion in the polymeric matrix and the resulting properties are strongly related to the homogeneity of the dispersion. In the present work, nylon 6.12 nanocomposites with aged pseudoboehmite were obtained using octadecylamine to improve the union between the polymer and the pseudoboehmite. The nanocomposites were characterized by thermal and mechanical test. The pseudoboehmite was characterized by scanning electron microscopy and x-ray diffraction. The nanocomposite was characterized by tensile strength test, 3 points bending test and impact Izod resistance test. The addition of pseudoboehmite promote the increase of the elasticity modulus evidencing the interaction of the pseudoboehmite with the polymeric matrix, probably modifying its crystalline structure. The addition of pseudoboehmite promoted an increase in the HDT an Vicat temperatures of the nanocomposite.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Influence of Concentration of Pseudoboehmite Nanofiller on the Thermal and
Mechanical Properties in Polystyrene Compounds
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Leila Figueiredo de Miranda, Antônio Hortêncio Munhoz Jr., Terezinha Jocelen Masson, Maura Vincenza Rossi
Polymeric nanocomposites are hybrid materials, where fillers with nanometric dimensions are dispersed in a polymeric matrix. The fillers have a high surface area, promoting better dispersion in the polymeric matrix and therefore an improvement in physical properties of the composite depending on the homogeneity of the material. In the present work, nanocomposites of polystyrene with different concentrations of pseudoboehmite obtained by a sol-gel process, and treated with octadecylamine were prepared. The nanocomposites were characterized by thermal and mechanical tests. The addition of pseudoboehmite caused a reduction of the melting flow during the production of the composites evidencing the interaction of pseudoboehmite with the polymeric matrix. The addition of pseudoboehmite promoted an increase in the melt flow index, in the the hardness of the nanocomposites obtained, practically does not affect the tensile strength and modulus and the impact strength decreases. The presence of pseudoboehmite causes increase in heat deflection temperature and Vicat softening point and the thermal decomposition occurred at a higher temperature than the pure PS.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Mutual Conversion between Stretched and Contracted Helices and its
External Stimuli Induced Drastic Colors and Geometrical Structures Changes
of Substituted Polyacetylenes Prepared with an Organo-Rhodium Catalyst
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Masayoshi Tabata, Yasuteru Mawatari, Yoshiaki Yoshida, Takahiro Sasaki
Unique conversions between stretched and contracted helices of mono-substituted polyacetylenes (SPA)s prepared with an organo rhodium complex-amine catalytic system were demonstrated. The conversions of aromatic SPAs with a drastic color change were caused by polymerization solvents used, substituents in the phenyl ring, and external stimuli like heat- and solvent-treatments which were induced in the solid state. The helices of aliphatic polyacetylenes was oscillating just like spring or coil which was synchronizing with the restricted rotation around the ester O-*C bond in the solution. The oscillation mode was named as an accordion-like helix oscillation “HELIOS”. All the conversions were attributed to the difference of the thermodynamical stability between stretched and contracted helices.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Electroactive Polymer Based Conducting, Magnetic, and Luminescent Triple
Composites
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Alexander V. Kukhta, Alesya G. Paddubskaya, Polina P. Kuzhir, Sergey A. Maksimenko, Svetlana A. Vorobyova, Stefano Bellucci, Pawan K. Khanna
The latest our results on triple polymer composites based on graphene nanoplatelets (GNP) covered by copper nanoparticles, iron oxide nanoparticles, and CdSe two-dimensional and spherical nanoparticles are presented and analyzed. It was found that GNP covered by copper nanoparticles results in higher conductivity and film stability increase in PEDOT:PSS than pure GNP. It was revealed that in magnetic field, composites based on GNP with iron oxide nanoparticles have metallic conductivity and form thin films with higher surface while thin films formed without magnetic field are dielectrics and have less surface. Luminescent composite based on CdSe nanoplatelets has been obtained. Two maxima in the luminescence spectra of CdSe nanoplatelets have been found and explained with a model based on efficient absorption of photons between neighbor nanoplatelets. Luminescence of active particles was different in different places of the sample and strongly depends on the graphene type. Stronger luminescence is observed in graphene with less amount of defects.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Effects of an External Magnetic Field on Polymeric Foam-Ferromagnet
Composites
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Marco D'Auria, Valentina Volpe, Daniele Davino, Roberto Pantani, Luigi Sorrentino
Composite lightweight materials based on a polymeric matrix with embedded magnetic micro-particles have been developed. The application of a magnetic field (MF) during the foaming of samples induced the alignment of magnetic particles along the MF lines, forming reinforcing chain-like structures. The presence of aligned micro-particles imparted an anisotropic mechanical behavior along the particle alignment direction, thus strongly improving mechanical stiffness and strength compared to randomly filled systems. The application of a MF on pre-strained samples during the magneto-mechanical characterization resulted in a direct relationship between the measured variation of the elastic modulus of the foam and the time dependent intensity of the applied MF (also for a magnetic field strength as low as 200 kA/m). In particular, all reinforced samples pre-strained in the linear elastic region of the stress-strain curve exhibited a magneto-strictive response (negative variation of the measured stress). On the contrary, a positive variation of the measured stress (strengthening effect) was detected in samples with aligned particles at pre-strains above the yield point. This behavior has been related to the tendency of chain-like aggregates in buckled cell edges to re-align along the MF lines.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Asymmetric Bilayer Artificial Muscles Based on Polypyrrole
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Masaki Fuchiwaki, Jose Gabriel Martínez, Toribio Fernandez Otero
The characteristics of the asymmetric artificial muscles, PPy-ClO4/tape, PPy-DBS/tape and PPy-ClO4/PPy-DBS worked in 0.5 M NaClO4 aqueous solutions were discussed by the dynamo-voltammetric responses, coulo-dynamic Evolution responses and the bending angle per unit of consumed charge and the cooperative dynamic effects of PPy-ClO4/PPy-DBS artificial muscles is clarified. In the PPy-ClO4/PPy-DBS asymmetric bilayer artificial muscles, the PPy-ClO4 layer shrinks and PPy-DBS layer swells during reduction and the PPy-ClO4 layer swells and PPy-DBS layer shrinks during oxidation. The artificial muscle originates cooperative dynamic bending actuation of the constituent layers (swelling/shrinking or shrinking/swelling) and achieves the larger bending amplitude than those of the PPy-ClO4/tape and the PPy-DBS/tape. The bending angle per unit of consumed charge on the PPy-ClO4/tape and PPy-DBS/tape is 3.240 and 2.85, respectively, and the cooperative dynamic effect on PPy-ClO4/PPy-DBS is 8.257. In case of NaCl having same level bending angle per unit of consumed charge on PPy-DBS/tape, 2.396, the cooperative dynamic effect on PPy-ClO4/PPy-DBS is just 3.868. Because the bending angle per unit of consumed charge on PPy-ClO4/tape is very low, 0.101. Actually, the cooperative dynamic effect on PPy-ClO4/PPy-DBS in Na2CO3 is 5.184 and is larger than that in NaCl even the bending angle per unit of consumed charge on PPy-DBS is lower than that on NaCl. The expansion and contraction of the PPy-ClO4 film dominates the reaction-driven bending motion and those of the PPy-DBS have a minor influence on the bending actuation.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• New Resonance Mode of Dielectric Elastomer Minimum Energy Structure
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Jian Wen Zhao, Yong Ge, Shu Wang, Bo Huang
The dielectric elastomer minimum energy structure (DEMES) can realize large angular deformations by a small voltage-induced strain of the dielectric elastomer, so it is a suitable candidate to make a rotary joint for a soft robot. Driven with an alternating electric field, the joint deformation vibrational frequency follows the input voltage frequency. However, the authors find that if the rotational angel over a negative angle during dynamic response, the resonance mode will be different from the traditional, the vibration with the largest amplitude does not occur while the voltage frequency is equal to natural response frequency of the joint. Rather, the vibrational amplitude will be quite large over a range of other frequencies, at which the voltage frequency is greater than one time of the nature frequency and smaller than two times. This phenomenon was analyzed by relationship between the bending angle, applied voltage and bending moment of the film to the frame on a timeline. This new resonance mode can be applied to some biomimetic soft robots that consist of DEMES rotary joint.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• IPMC Actuators Fabricated Using MEMS Technology
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Shigeki Tsuchitani, Kunitomo Kikuchi, Ippei Shimizu, Tomohisa Taniguchi, Hirofumi Miki
Fabrication of ionic polymer metal composite (IPMC) on Si substrate and micromachining of IPMC are basic technologies for developing MEMS devices using IPMC. Adhesion of IPMC with the substrate is essential to fabricate IPMC on the substrate. Swelling of IPMC with water makes IPMC peel from the substrate due to the internal stress. To enlarge adhesion force of IPMC with the Si substrate, we have fabricated IPMC on an anodic-oxidized porous Si surface, which dramatically increased adhesion area between the IPMC and the substrate. Fabricated IPMC didn't peel from the Si substrate during the operation in water. Photolithography is a key technology in MEMS fabrication. However, water and organic solvents used in the fabrication process also swell IPMC and lower machining accuracy. We have developed a machining technology of microminiaturized IPMC by mainly using dry processes: reactive ion etching of Nafion film through metal mask, and a selective electrode formation using a plasma irradiation on Nafion and an electroless gold plating. An array of IPMCs with a width of 100 μm was fabricated and their operations in water were confirmed.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Elastomer Transducers
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Seiki A. Chiba, Mikio Waki, Yoshinori Tanaka, Naoaki Tsurumi, Kuniyoshi Okamoto, Kazuya Nagase, Masatoshi Honma, Hideyuki Yokota, Keiichi Odagiri, Hiromi Sato, T. Saiki, Junya Kaneko
Electroactive polymer transducers have many features that are desirable for various devices. An especially attractive type of electroactive polymer is dielectric elastomer (DE).
Our recent progress is a DE actuator having only 0.1 g of DE that lifted a weight of 2 kg using carbon system electrodes. We also developed a ribbon form DE actuator having a sensor function that can be used to measure force, or pressure, as well as motion at the same time. This actuator can assist human and robot motions. At the same time, it can work as a motion feedback sensor. We hope that it may be useful for smart rehabilitation equipment for hands, legs, and fingers.
DE has also been shown to operate in reverse as a generator. Experiments have been performed on portable DE generators/wearable generators powered by human motion, ocean wave power harvesters mounted on buoys, solar heat generators, and water turbines. While the power output levels of such demonstration devices is small, the performance of these devices has supported the potential benefits of DE.
We are developing elastomers having larger dielectric constant using barium titanium oxide to produce a “super artificial muscle for energy harvesting devices, actuators & sensors” in the near future.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Efficient Linear Approach for the Closed-Loop Control of a Ionic Polymer
Bending Actuator
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Bertrand Tondu, Aiva Simaite, Ganesh Kumar Hari Shankar Lal Das, Philippe Soueres, Christian Bergaud
Tri-layer electroactive bending polymeric artificial muscles generally exhibit no overshoot during open-loop step response with a non-zero initial slope when the output is the vertical position of the bending sample tip. We propose to identify such a bending step contraction by a nonlinear system derived from a linear first order system in the form: where the parameters k, T and r depend on the u-control voltage. We show the relevance of this approach for identifying the step-response of a PEDOT:PSS/PVDF/ionic liquid actuator developed at the laboratory. As a consequence, we try to show that a linear PI-controller, including voltage constraints, is a simple and an efficient approach for a closed-loop control of the bending actuator.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Humanoids and the Potential Role of Electroactive Materials/Mechanisms in
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Yoseph Bar-Cohen
Humanoids are increasingly becoming capable biologically inspired robots that are appearing and behaving lifelike. Making humanlike robots is the ultimate challenge to biomimetics and, while for many years they were considered a science fiction, such robots are increasingly becoming engineering reality. Progress in producing such robots are allowing them to perform impressive functions and tasks. In 2012, in an effort to promote significant advances in developing humanoids, DARPA posed a Robotic Challenge to produce such robots that operate in disaster scenarios towards making society more resilient. The challenge was focused on the requirements that have been needed after the Fukushima accident in Japan, hoping to advance the field of disaster robotics. This disaster posed significant challenges to emergency responders since radiation prevented people from going into the station and venting the explosive gas. Another significant development in this field is the fact that major US corporations have entered into the race to produce commercial humanoids. As a result, one can expect significant and rapid progress in this field. Developing humanoids is critically dependent of the use of highly efficient, compact, lightweight actuators and electroactive materials are offering great potential. This paper reviews the state-of-the-art of humanlike robots, potential applications and challenges, as well as the actuation materials that are used or could be used.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Novel Behavior in Smart Polymeric Materials: Stress Memory and its
Potential Applications
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Jin Lian Hu, Harishkumar Narayana
Materials, structures and systems, responsive to an external stimulus are smart and adaptive to our human demands. Among smart materials, polymers with shape memory effect are at the forefront of research leading to comprehensive publications and wide applications. In this paper, we extend the concept of shape memory polymers to stress memory ones, which have been discovered recently. Like shape memory, stress memory represents a phenomenon where the stress in a polymer can be programmed, stored and retrieved reversibly with an external stimulus such as temperature and magnetic field. Stress memory may be mistaken as the recovery stress which was studied quite broadly. Our further investigation also reveals that stress memory is quite different from recovery stress containing multi-components including elastic and viscoelastic forces in addition to possible memory stress. Stress memory could be used into applications such as sensors, pressure garments, massage devices, electronic skins and artificial muscles. The current revelation of stress memory potentials is emanated from an authentic application of memory fibres, films, and foams in the smart compression devices for the management of chronic and therapeutic disorders.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Two-Way Shape Memory Behavior of Electrospun Non-Woven Mats Prepared from
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Stefano Pandini, Silvia Agnelli, Andrea Merlettini, Chiara Gualandi, Maria Letizia Focarete, Katia Paderni, Massimo Messori, Maurizio Toselli
Non-woven fibrous mats based on semicrystalline networks were prepared starting from poly(ε-caprolactone) and by combining electrospinning process and sol-gel crosslinking reaction. The mats were subjected to proper thermo-mechanical cycles to investigate their two-way shape memory capabilities (i.e. the possibility to change between two distinguished shapes upon heating and cooling), and an improvement of the two-way behaviour was researched through the application of a training cycle. An ex-situ SEM analysis described the microstructural evolution accompanying the two-way shape memory cyclic response.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Fractional Calculus Approach to Relaxation Behavior of Amorphous Shape
Memory Polymers
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Chang Qing Fang, Hui Yu Sun, Jian Ping Gu
To select an appropriate relaxation kernel function is significant for shape memory polymers (SMPs) in their thermomechanical constitutive models. The relaxation modulus of SMPs are described by fractional-order viscoelastic (FOV) kernel and three other kinds of viscoelastic kernel, that is, Prony series, Kohlrausch-Williams-Watts (KWW) kernel and Cole-Cole Model (CCM) kernel. The data fitting result shows FOV kernel is a valuable tool to describe the relaxation response of SMPs. Compared with Prony series, KWW kernel and CCM kernel, the FOV kernel can give a comparative description of relaxation modulus of SMPs with fewer material parameters.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Role of Interstitial Oxygen Atom on Martensitic Transformation of Ti-Nb
Alloy
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Masaki Tahara, Tomonari Inamura, Hee Young Kim, Shuichi Miyazaki, Hideki Hosoda
The effect of oxygen content on the stability of α′′ martensite phase of the Ti-20mol%Nb alloy was investigated by differential scanning calorimetry. The reverse martensitic transformation temperature increased with increasing oxygen content, and this means that α′′ martensite phase was stabilized by oxygen addition. The mechanism of α′′ martensite stabilization by oxygen atoms was discussed based on the changes in the lattice parameters of α′′ martensite.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• The Magnetic States of Co- and Cr-Doped Ni-Mn-(In, Sn) Heusler Alloys
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Vasiliy D. Buchelnikov, Vladimir V. Sokolovskiy, Mikhail A. Zagrebin, Peter Entel
In this paper we report on the equilibrium magnetic and structural reference states of complex Cr doped Ni-Co-Mn-(In, Sn) Heusler alloys, which are studied from first-principles within the density functional theory. The off-stoichiometric compositions were treated by using the supercell approach. Three different ferrimagnetic and one ferromagnetic spin configurations were considered. The results of energy relaxation calculations have been averaged over different atomic distributions. It is found that Ni14Co2Mn11Cr1(In, Sn)4 the ferromagnetic (a ferrimagnetic) spin configuration in austenite (martensite) is energetically stable, respectively.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• First-Principles and Monte Carlo Studies of Magnetocaloric Effects
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Peter Entel, Anjana Talapatra, Raymundo Arroyave, Navdeep Singh, Markus Gruner, Richard Dronskowski, Dimitri Bogdanovski, Alfred Hucht
We have performed \textit{ab initio} electronic structure calculations and Monte Carlo simulations of magnetically frustrated intermetallic materials where complex magnetic configurations and chemical disorder lead to rich phase diagrams. With lowering of temperature, we find for magnetic Heusler alloys a ferromagnetic phase which transforms to an antiferromagnetic phase at the magnetostructural phase transition and to a cluster spin glass at still lower temperatures. We discuss chemical bonding features of Ni$_2$MnGa and the giant magnetocaloric effec of Ni-Mn-In with Co and Cr substitution as well as the origin of the magnetostructural transition.The numerical simulations allow a complete characterization of the magnetically frustrated materials.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Effects of Pseudoelastic Cycling under Different Temperatures on Physical
and Mechanical Properties of a NiTi Alloy
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Mariana Carla Mendes Rodrigues, Guilherme Corrêa Soares, Vicente Tadeu Lopes Buono, Leandro de Arruda Santos
The effects of pseudoelastic cycling under different temperatures on physical and mechanical properties of a NiTi superelastic wire were investigated by uniaxial tensile testing. The samples were cyclically deformed up to 6% strain under several test temperatures above the austenite finish temperature (Af). In order to approach a cyclic saturation level, number of cycles was established as 20. The temperature at which mechanical cycling was performed played a strong role on residual strain, dissipated energy and also on the critical stress to induce martensite, being consistent with the Clausius-Clapeyron relationship. It was found that an increase in test temperature resulted in more significant changes in the alloy’s functional behavior, but cyclic stability tended to be reached within fewer cycles. X-ray diffraction results showed that no martensite was stabilized at any condition and that austenite diffraction peaks intensities increased with test temperature, which was attributed to stress relaxation. Tensile tests until rupture and three point bending tests revealed that the mechanical response of the specimens cycled at higher temperatures and as received were fairly similar, and that specimens cycled at lower temperatures exhibited a slightly higher flexibility.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Mechanical and Superelastic Properties of Au-51Ti-18Co Biomedical Shape
Memory Alloy Heat-Treated at 1173 K to 1373 K
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Taywin Buasri, Hyunbo Shim, Masaki Tahara, Tomonari Inamura, Kenji Goto, Hiroyasu Kanetaka, Yoko Yamabe-Mitarai, Hideki Hosoda
The effect of heat treatment temperature from 1173 K to 1373 K for 3.6 ks on mechanical and superelastic properties of an Ni-free Au-51Ti-18Co alloy (mol%) was investigated. The stress for inducing martensitic transformation (SIMT) and the critical stress for slip deformation (CSS) slightly decrease with increasing the heat–treatment temperature. Regardless of heat–treatment temperature, good superelasticity was definitely recognized with the maximum shape recovery ratio up to 95 % and 4 % superelastic shape recovery strain. As the mentioned reasons, the Au-51Ti-18Co alloy is promising for practical biomedical applications.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Mechanical Properties of Nanoceramic Zirconia Coatings on NiTi Orthodontic
Wires
• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Natalia Isabel de Azevedo Lopes, Leandro de Arruda Santos, Vicente Tadeu Lopes Buono
Nickel-titanium (NiTi) alloys have been largely applied in biomedical devices due to their special properties of superelasticity and shape memory. Even though NiTi generally displays good corrosion resistance and biocompatibility, mechanical fatigue and fretting-corrosion resistance remain important challenges in a number of applications, since it can accelerate nickel ions releasing, that have been reported as cytotoxic, mutagenic, and allergenic. This study aims to develop an appropriate coating to help delaying crack nucleation and corrosion in NiTi alloys. Zirconia (ZrO2) coating stands as a good candidate to improve the corrosion and wear resistance of metallic substrates and, in this work, it was obtained by electrodeposition on NiTi superelastic and shape memory orthodontic wires. The surface morphology and the chemical composition of the coated samples were evaluated using scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), and atomic force microscopy (AFM). The mechanical response was evaluated by three-point bending tests. The results showed that the ZrO2 layer was uniform and well adhered to the NiTi subtract. Additionally, it was observed that this coating was capable of undergoing severe deformation without cracking, indicating a potential increase in fatigue resistance of the conjugate.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

• Structural Effects of Thermomechanical Processing on the Static and

• Abstract: Publication date: 31 October 2016
Source: Advances in Science and Technology Vol. 97
Author(s): Elena Mihalache, Bogdan Pricop, Radu Ioachim Comăneci, Marius Gabriel Suru, Nicoleta Monica Lohan, Mihai Mocanu, Burak Özkal, Leandru Gheorghe Bujoreanu
Fe-14Mn-6Si-9Cr-5Ni (wt. %) shape memory alloys (SMAs) were produced by powder metallurgy (PM) combined with Mechanical Alloying (MA). The specimens were pressed and sintered under Ar atmosphere from as blended powders as well as from mixtures of as blended and 10, 20, 30 and 40 vol. % MA’ed powders, respectively. The five groups of sintered specimens were hot-rolled, spark-erosion cut and solution treated at five temperatures (923, 1023, …, 1373K/ 300 s/ water). Tensile loading-unloading tests were performed in order to obtain stress-induced martensite at different pre-straining degrees. The static responses of the twenty five types of specimens were evaluated by means of the surface areas under unloading curve (E2) and between loading and unloading curves (E1) which were used for determining static internal friction, Q-1. The dynamic responses of the undeformed specimens were determined by Dynamic Mechanical Analysis (DMA) performed at room temperature with a three-point-bending specimen holder in strain sweep mode. The structure of the twenty five specimens was analyzed X-ray diffraction. The effects of MA fraction were correlated with static and dynamic responses via structural changes.

PubDate: Mon, 31 Oct 2016 00:00:00 +010

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