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1.
Langmuir ; 33(27): 6739-6750, 2017 07 11.
Artículo en Inglés | MEDLINE | ID: mdl-28605897

RESUMEN

We explore the suitability of nanocomposite thin films based on laponite nanomaterial and grafted antiadhesive polymers as transparent nonfouling surfaces. For this purpose, two polymers were chosen: a linear poly(ethylene glycol) (PEG) silane, 2-[methoxy(polyethyleneoxy)propyl]-trimethoxysilane), and thermoresponsive poly(oligo ethylene glycol)-methyl ether-methacrylate (POEGMA) brushes. PEG silane was grafted on the laponite nanoparticles in solution yielding homogeneous and transparent thin films via a dip coating procedure on glass and silicon substrates. POEGMA was grafted on laponite-(3-Aminopropyl)trimethoxysilane (APTMS) nanocomposite films that were processed similarly to PEG-silane using atom transfer radical polymerization (ATRP). Film characterization with, among others, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM) attests to successful grafting of the polymers to the laponite nanoparticles. In particular, evidence of basal plane expansion of laponite with increasing silane concentration are obtained using XRD, while patent morphological changes are revealed with AFM. The results are discussed in terms of the different grafting sites on laponite and compared with literature. While LP-PEG-silane is easily applied to a surface from a precursor solution via a dip coating procedure LP-APTMS-OEGMA requires lots more chemicals, a thorough control of reaction parameters, and longer reaction time in order to generate films with the desirable properties. We therefore also addressed the antifouling properties of the films. These were tested together with control samples of bare glass and laponite thin films for 30 days in an algae container. More tests were conducted with fibroblast cell cultures. Our preliminary results show that grafting of PEG containing polymers and polymer brushes alters the properties of the laponite films from fouling to nonfouling surfaces. As a first estimate, the adhesion of particles (diatoms, algae, etc.) to surfaces is reduced by approximately 85% in the case of LP-PEG-silane and up to 92% in the case of LP-APTMS-POEGMA, in comparison to the control surfaces. Furthermore, practically no cell adhesion on such surfaces could be observed.

2.
Langmuir ; 32(27): 6985-90, 2016 07 12.
Artículo en Inglés | MEDLINE | ID: mdl-27315420

RESUMEN

Large-area ordered nanorod (NR) arrays of various functional materials can be easily and cost-effectively processed using on-substrate anodized porous aluminum oxide (PAO) films as templates. However, reproducibility in the processing of PAO films is still an issue because they are prone to delamination, and control of fabrication parameters such as electrolyte type and concentration and anodizing time is critical for making robust templates and subsequently mechanically reliable NR arrays. In the present work, we systematically investigate the effects of the fabrication parameters on pore base morphology, devise a method to avoid delamination, and control void formation under the barrier layer of PAO films on gold underlayers. Via systematic control of the anodization parameters, particularly the anodization current density and time, we follow the different stages of void development and discuss their formation mechanisms. The practical aspect of this work demonstrates how void size can be controlled and how void formation can be utilized to control the shape of NR bases for improving the mechanical stability of the NRs.

3.
Nanomaterials (Basel) ; 14(9)2024 Apr 27.
Artículo en Inglés | MEDLINE | ID: mdl-38727364

RESUMEN

Density functional theory (DFT) calculations of hydrogen adsorption on titanium nitride had previously shown that hydrogen may adsorb on both titanium and nitrogen sites with a moderate adsorption energy. Further, the diffusion barrier was also found to be low. These findings may qualify TiN, a versatile multifunctional material with electronic conductivity, as an electrode material for the hydrogen evolution reaction (HER). This was the main impetus of this study, which aims to experimentally and theoretically investigate the electrocatalytic properties of TiN layers that were processed on a Ti substrate using reactive ion sputtering. The properties are discussed, focusing on the role of oxygen defects introduced during the sputtering process on the HER. Based on DFT calculations, it is shown that these oxygen defects alter the electronic environment of the Ti atoms, which entails a low hydrogen adsorption energy in the range of -0.1 eV; this leads to HER performances that match those of Pt-NPs in acidic media. When a few nanometer-thick layers of Pd-NPs are sputtered on top of the TiN layer, the performance is drastically reduced. This is interpreted in terms of oxygen defects being scavenged by the Pd-NPs near the surface, which is thought to reduce the hydrogen adsorption sites.

4.
Micromachines (Basel) ; 14(6)2023 May 28.
Artículo en Inglés | MEDLINE | ID: mdl-37374726

RESUMEN

Noble metal nanoparticles and multi-materials thereof are processed on a substrate from aqueous solutions of the metallic ions, precluding any chemical additives/catalysts. The methods reported here take advantage of interactions between collapsing bubbles and the substrate that result in the generation of reducing radicals at the substrate surface and leading to the reduction of the metal ions on those sites, followed by nucleation and growth. Two selected substrates where these phenomena take place are nanocarbon and TiN. By either using ultrasonic radiation of the substrate in ionic solution or quenching the substrate in a solution from temperatures above the Leidenfrost temperature, a high density of nanoparticles of Au, Au/Pt, Au/Pd and Au/Pd/Pt are synthesized on the substrate surface. The sites where the reducing radicals are generated determine the self-assembly of the nanoparticles. The methods yield highly adherent surface films and nanoparticles; they are materials efficient and cost effective because only the surface is modified with costly materials. The formation mechanisms of these green multi-material NPs are described. Outstanding electrocatalytic performances in acidic solutions of methanol and formic acid are demonstrated.

5.
Nanomaterials (Basel) ; 13(13)2023 Jul 05.
Artículo en Inglés | MEDLINE | ID: mdl-37446522

RESUMEN

Ordered thin films of Au nanorods (NRs) on Ti/Au/Si heterostructure substrates are electrodeposited in thin film aluminum oxide templates and, after template removal, serve as supports for Pd and Pt nanocatalysts. Based on previous work which showed a better electrocatalytic performance for layered Au/Pd nanostructures than monolithic Pd, electrodeposited 20 nm Pd discs on Au-NRs are first investigated in terms of their catalytic activity for the hydrogen evolution reaction (HER) and compared to monolithic 20 nm Pd and Pt discs. To further boost performance, the interfacial interaction area between the Au-NRs supports and the active metals (Pt and Pd) was increased via magnetron sputtering an extremely thin layer of Pt and Pd (20 nm overall sputtered thickness) on the Au-NRs after template removal. In this way, the whole NR surface (top and lateral) was covered with Pt and Pd nanoparticles, ensuring a maximum interfacial contact between the support and the active metal. The HER performance obtained was substantially higher than that of the other nanostructures. A Salient result of the present work, however, is the superior activity obtained for sputtered Pd on Au in comparison to that of sputtered Pt on Au. The results also show that increasing the Au-NR length translates in a strong increase in performance. Density functional theory calculations show that the interfacial electronic interactions between Au and Pd lead to suitable values of hydrogen adsorption energy on all possible sites, thus promoting faster (barrier-free diffusion) hydrogen adsorption and its recombination to H2. A Volmer-Heyrovsky mechanism for HER is proposed, and a volcano plot is suggested based on the results of the Tafel plots and the calculated hydrogen adsorption energies.

6.
Micromachines (Basel) ; 14(8)2023 Aug 20.
Artículo en Inglés | MEDLINE | ID: mdl-37630180

RESUMEN

Nickel hydroxide ß-Ni(OH)2 nanolamellae with high aspect ratios were grown via chemical bath deposition (CBD) on both smooth and textured nickel foil. Depending on bath composition and/or the presence of an additive, thin foam-like nanolamellae to stacked lamellae were obtained. The used CBD method is highly cost-effective, as it is faster and requires less chemicals than typical hydrothermal methods, and it is readily implementable for large-scale production. The influence of surface texture on the final morphology and its effect on capacitive performance was investigated. Herein, we show how subtle changes in the concentration can drastically influence the morphology, which, in turn, drastically impacts the supercapacitive performance of the electrode. Also, the use of a textured surface significantly impacts the morphology, with vastly better cycling performance than samples made on a relatively smooth substrate. The measured specific capacitance values of the best sample were 1961 Fg-1 at 5 mVs-1 and 1998 Fg-1 at 1 Ag-1 under potentiostatic and galvanostatic conditions, respectively. This sample also retained 100% of its initial specific capacitance when discharged at a very high current density of 40 Ag-1. These values are substantially enhanced compared to previously reported data using a nearly analogous method (CBD with higher reagent conc.), with our method, cost-wise, offering economic advantages relative to results obtained with similar materials and other methods (e.g., hydrothermal).

7.
Langmuir ; 28(16): 6706-13, 2012 Apr 24.
Artículo en Inglés | MEDLINE | ID: mdl-22468776

RESUMEN

A sol-gel chemistry approach is employed to generate mesoporous and macroporous brookite thin films using Ag ions as dopant species whose thermal stability is well above previously reported literature values for thin films. The Ag ions not only induce the formation of brookite but also participate in its enhanced thermal stability. Despite brookite being metastable in nature, which renders it a challenge to synthesize, it has been prescribed as a potential competitor to anatase. We have used a layer-by-layer approach to generate a mesoporous Ag-doped brookite structure at 500 °C with 95% composition by XRD. This tightly packed mesoporous structure can be described as striated grains of brookite protruding from the surface to form an interlocked network whose thermal stability spans up to 800 °C. The open structure of brookite makes it an apt host for the intercalant Ag species, whose inclusion within the brookite framework is improved by the presence of a stabilizing agent. Both the morphology of the surface and the presence of a stabilization agent for Ag contribute to enhancing its thermal stability. This is in contrast to the thermal stability of the macroporous brookite thin film, which was found to be lower (<700 °C) than that of the mesoporous brookite thin film. The reagents are deliberately chosen to produce a macroporous film in the absence of a stabilizing agent. Ag nodules are observed to be formed at 700 °C, which implies their limited intercalation into the brookite structure, thus rendering them relatively less stable. Moreover, the macroporous film being relatively more relaxed is more susceptible to phase transformation at a higher calcination temperature. Our results provide a platform that paves the way toward better control, thereby leading to a broader technological application of brookite.

8.
ACS Appl Mater Interfaces ; 12(13): 14983-14992, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32069393

RESUMEN

Au nanoparticle (NP) decorated heterogeneous TiO2 catalysts are known to be effective in the degradation of various organic pollutants. The photocatalytic performance of such Au-TiO2 structures remarkably depends on the size, morphology, and surface coverage of the Au NPs decorating TiO2. Here we propose an effective way of preparing a highly active Au nanocluster (NC) decorated TiO2 thin film by a novel photodeposition method. By altering the solvent type as well as the illumination time, we achieved well-controlled surface coverage of TiO2 by Au NCs, which directly influences the photocatalytic performance. Here the Au NCs coverage affects both the electron store capacity and the optical absorption of the hybrid Au-TiO2 system. At low surface coverage, 19.2-29.5%, the Au NCs seem to enhance significantly the optical adsorption of TiO2 at UV wavelengths which therefore leads to a higher photocatalytic performance.

9.
Ultrason Sonochem ; 51: 138-144, 2019 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-30385243

RESUMEN

The sonochemical processing of nanomaterials in a solution is well established and has been advantageously used for a variety of nanomaterials and morphologies thereof. In general, high energy and high frequency ultrasound is applied to a solution containing the ionic species of the elements to be reduced as well as a certain amount of reducing chemicals. For further applications such as catalysis washing, filtering, dispersion and mounting on or mixing in a substrate are necessary. A sonochemical processing of nanomaterials directly on a substrate could make all these steps obsolete. Herein we show that noble metal and nanoalloy nanoparticles (NPs) can directly be processed on nanocarbon and titanium nitride surfaces using a simple ultrasound laboratory cleaner in aqueous solutions that are free from any reducing chemicals. The process is demonstrated on Au-NPs and nanoalloys of AuPd and PdPt which form a dense distribution on the substrate surface. To illustrate the catalytic activity of the NPs, the electrocatalytic performance of one AuPd-nanoalloy is demonstrated. The results are discussed in terms of reduction phenomena occurring at the interface between the ultrasonic cavitation and the substrate. We think that these reduction phenomena are mediated by the formation of reducing radicals at the substrate surface that are in turn driven by OH radicals from water sonolysis. Electrochemical current measurement at 0 V seem to support the existence of reducing currents during measurements under chopped ultrasound in an aqueous solution of HAuCl4 in comparison to measurements in water.

10.
Data Brief ; 23: 103702, 2019 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-30828598

RESUMEN

The data presented in this article affords insight into the fabrication and ensuing microstructure of the supported porous anodic aluminum oxide (AAO) and TiO2-nanotubes (NT) films that are used for the subsequent grafting of antifouling poly(oligo ethyleneglycol) methylether methacrylate (POEGMA) and poly acrylamide (PAAm) brushes. The experimental procedure for the grafting of POEGMA and PAAm via atom transfer radical polymerization (ATRP) is described in Wassel et al. (2019) https://doi.org/10.1016/j.matdes.2018.107542 [1]. The FTIR spectra of the porous oxides before and after attachment of (3-Aminopropyl)trimethoxysilane (APTMS) are presented. Microscopic images of thick POEGMA films and PAAm on AAO are displayed, and an FTIR spectrum of AAO/PAAm is shown. An EDX mapping of carbon is shown on an AAO/POEGMA sample. The adsorption behavior of Fluorescein isothiocyanate (FITC) marked bovine serum albumin (BSA) on patterned porous TiO2-NT films is documented. Finally microscopic images are presented to compare the scratch resistance behavior of pristine porous films with those functionalized with POEGMA.

11.
Nanomaterials (Basel) ; 10(1)2019 Dec 27.
Artículo en Inglés | MEDLINE | ID: mdl-31892203

RESUMEN

Interdiffusion between Si substrate and nanorod arrays of Au, Pt, and AuPt nanoalloys is investigated at temperatures lower than the AuSi eutectic temperature. When the nanorod is pure Au, Si diffusion from the substrate is very rapid. Au atoms are completely replaced by Si, converting the nanostructure into one of Si nanorod arrays. Au is diffused out to the substrate. The Au nanorod arrays on Si are unstable. When the nanorod is pure Pt, however, no diffusion of Si into the nanorod or any silicide formation is observed. The Pt nanorods are stable on Si substrate. When the nanorods are an alloy of AuPt, interesting interactions occur. Si diffusion into the nanorods is rapid but the diffusing Si readily reacts with Pt forming PtSi while Au diffuses out to the substrate. After annealing, nanophases of Au, Pt, PtSi, and Si may be present within the nanorods. When the Pt content of the alloy is low (12 at%) all Pt atoms are converted to silicide and the extra Si atoms remain in elemental form, particularly near the tip of the nanorods. Hence, the presence of Au accelerates Si diffusion and the ensuing reaction to form PtSi, a phenomenon absents in pure Pt nanorods. When the Au content of the alloy is low, the Si diffusion would cease when all Au atoms have diffused out of the nanorod, thereby arresting the silicide formation resulting in excess Pt in elemental form within the nanorod. This is a technique of making Si nanorods with and without embedded PtSi nanophase consisting of heterojunctions which could have unique properties.

12.
J Biomed Mater Res A ; 80(1): 159-66, 2007 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-17001650

RESUMEN

In the present study the in vitro biocompatibility of electropolished NiTi sheets is investigated. The assessment of cytotoxic effects due to potential Ni leaching from metal sheets was performed in direct contact with primary human fibroblast cultures using the 5-bromo-2'-deoxyuridine cell proliferation assay and morphologic studies via light microscopy and scanning electron microscopy. To assess toxic effects related to Ni-ions release, cells cultured in the presence of increasing concentrations of Ni(2+) (NiSO(4).6H(2)O) served as positive controls. It is shown that while the addition of NiSO(4) caused severe proliferation decrease (approximately 80%) and morphologic damage at a concentration of 50 mg/L Ni(2+) no negative effects were observed in fibroblasts cultured in the presence of electropolished NiTi sheets. The results are discussed in terms of surface topography effects on the biocompatibility of NiTi shape memory alloys.


Asunto(s)
Aleaciones , Proliferación Celular , Fibroblastos/citología , Encía/citología , Ensayo de Materiales , Níquel , Titanio , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Humanos , Irritantes/farmacología , Níquel/farmacología , Propiedades de Superficie
13.
Environ Sci Pollut Res Int ; 24(2): 1442-1449, 2017 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-27783247

RESUMEN

Electrochemical oxidative degradation of diazo dye Amido black 10B (AB10B) as model pollutant in water has been studied using nanostructured ZnO-TiO2 thin films deposited on graphite felt (GrF) substrate as anode. The influence of various operating parameters, namely the current intensity, the nature and concentration of catalyst, the nature of electrode materials (anode/cathode), and the adsorption of dye and ambient light were investigated. It was found that the oxidative degradation of AB10B followed pseudo first-order kinetics. The optimal operating conditions for the degradation of 0.12 mM (74 mg L-1) dye concentration and mineralization of its aqueous solution were determined as GrF-ZnO-TiO2 thin film anode, 100 mA current intensity, and 0.1 mM Fe2+ (catalyst) concentration. Under these operating conditions, discoloration of AB10B solution was reached at 60 min while 6 h treatment needed for a mineralization degree of 91 %. Therefore, this study confirmed that the electrochemical process is effective for the degradation of AB10B in water using nanostructured ZnO-TiO2 thin film anodes.


Asunto(s)
Negro de Almidón/aislamiento & purificación , Electrodos , Titanio/química , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodos , Óxido de Zinc/química , Adsorción , Compuestos Azo/química , Catálisis , Grafito/química , Cinética , Naftalenosulfonatos/química , Oxidación-Reducción
14.
Chem Commun (Camb) ; 51(71): 13650-3, 2015 Sep 14.
Artículo en Inglés | MEDLINE | ID: mdl-26226291

RESUMEN

An efficient and easy method is described which allows modification of supported nanocarbon films with carbon nanotubes (CNTs) from an aqueous colloidal suspension. Subsequently CNTs can be decorated with Pt-nanoparticles directly from an aqueous solution of Pt ions without the need for reducing agents. High performance supercapacitors and electrocatalysts are obtained.

15.
Biomaterials ; 23(14): 2871-8, 2002 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-12069327

RESUMEN

In the present paper, the effects of polyacrylic acid (PAA) conditioning on the morphology and chemistry of bovine enamel surface and the resulting interfacial reactions are being investigated using photometric, microscopic (SEM, AFM), electron spectroscopic (XPS) and staining methods (neutral red dye). The results are compared to two reference surfaces obtained by simple grinding and by etching with a phosphoric acid solution. It is shown that PAA conditioning leads to the leaching of calcium and phosphorus ions, to the smoothening of the surface and probably to the formation of a polymeric film at the surface. A mechanism by which a preliminary PAA conditioning of the enamel leads to the reported higher bonding strength between enamel and glass ionomer cements is proposed.


Asunto(s)
Resinas Acrílicas , Esmalte Dental/metabolismo , Grabado Ácido Dental , Animales , Calcio/metabolismo , Carbono/metabolismo , Bovinos , Esmalte Dental/ultraestructura , Durapatita/metabolismo , Geles , Humanos , Indicadores y Reactivos/metabolismo , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Rojo Neutro/metabolismo , Oxígeno/metabolismo , Fósforo/metabolismo , Propiedades de Superficie
16.
Biomaterials ; 23(14): 2887-94, 2002 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-12069329

RESUMEN

The present paper compares the transformation behaviour and mechanical properties of two orthodontic wires of close chemical compositions. The effects of surface topography and surface finish residues on the potentiodynamic corrosion behaviour and biocompatibility are also reported. The cytotoxicity tests were performed on both alloys in fibroblast cell cultures from human gingiva using the MTT test. It is shown that the surface finish and the amounts of surface finish residues affect dramatically the corrosion resistance. Bad surface finish results in lower corrosion resistance. The in vitro biocompatibility, though not affected to the extent of corrosion resistance, is also reduced as the surface roughness and the amounts of residues increase. This is thought to be due to surface effects on corrosion and metallic ions release.


Asunto(s)
Aleaciones/química , Materiales Biocompatibles/química , Alambres para Ortodoncia , Rastreo Diferencial de Calorimetría , Células Cultivadas , Corrosión , Fibroblastos/citología , Fibroblastos/metabolismo , Encía/citología , Humanos , Técnicas In Vitro , Microscopía Electrónica de Rastreo , Níquel/química , Estrés Mecánico , Propiedades de Superficie , Titanio/química
17.
J Orofac Orthop ; 64(1): 16-26, 2003 Jan.
Artículo en Inglés, Alemán | MEDLINE | ID: mdl-12557104

RESUMEN

AIM: The aim of the present investigation was to contribute to an understanding of the effects of surface topography and chemical composition on the corrosion behavior and thus the biocompatibility of Elgiloy (RMO, Denver, CO, USA), a common Co-based alloy. MATERIAL AND METHODS: The results are compared with those obtained for a binary NiTi alloy, Neo Sentalloy (GAC, Central Islip, NY, USA) and a beta-III-Ti alloy, TMA (Ormco, Glendora, CA, USA). In the present study, the surface topography and the chemical composition of two different grades of Elgiloy, Blue Elgiloy (soft) and Yellow Elgiloy (ductile), were examined by means of scanning electron microscopy (SEM) and energy-dispersive spectroscopy analysis (EDS). Their corrosion behavior in half-strength Ringer solution and in an artificial saliva solution according to Barrett [1] was investigated using potentiodynamic corrosion testing (PDC). The photometry-based PAN method was used to quantify the released Ni and Co ions. The in vitro biocompatibility of the two grades of Elgiloy was tested in three different cell cultures: in L929, a commercially available mouse fibroblast cell line, and in primary human epithelial cells and fibroblasts. RESULTS: The results of the corrosion testing showed satisfactorily high pitting corrosion potentials but lower repassivation potentials and a strong increase in current density once pitting had occurred. The photometric results revealed the release of Ni and Co ions in both tested electrolytes. The tested native surfaces exhibited numerous grinding and polishing grooves, inclusions and inhomogeneities of the microstructure. After corrosion testing the same surfaces displayed numerous signs of corrosion, especially in areas with microstructural inhomogeneities. In vitro biocompatibility testing showed a substantially reduced dehydrogenase activity in the presence of Elgiloy. The reduced quality of surface finish resulting from the manufacturing process led in the case of the tested Elgiloy types to decreased corrosion resistance with consequently reduced in vitro biocompatibility. CONCLUSIONS: In this context it is also conceivable that patients with a proven allergy to nickel, cobalt or chromium may react sensitively to the deployment of this alloy, at least in the surface quality tested by us. From this aspect, the introduction of a binding standard for the surface quality of materials used in orthodontic appliances is urgently recommended.


Asunto(s)
Aleaciones de Cromo , Cobalto , Aleaciones Dentales , Ensayo de Materiales , Alambres para Ortodoncia , Animales , Línea Celular , Aleaciones de Cromo/química , Aleaciones de Cromo/toxicidad , Cobalto/química , Cobalto/toxicidad , Aleaciones Dentales/química , Aleaciones Dentales/toxicidad , Humanos , Técnicas In Vitro , Ratones , Microscopía Electrónica de Rastreo , Alambres para Ortodoncia/efectos adversos , Espectrofotometría , Propiedades de Superficie
18.
J Orofac Orthop ; 64(2): 88-99, 2003 Mar.
Artículo en Inglés, Alemán | MEDLINE | ID: mdl-12649705

RESUMEN

PURPOSE: The aim of this study was to characterize five selected commercial NiTi archwires in terms of their transformation behavior, chemical composition, surface topography and mechanical properties (at temperatures of 22 degrees C, 37 degrees C and 60 degrees C). MATERIAL AND METHODS: The rectangular orthodontic archwires investigated were Neo Sentalloy F80 (GAC, Central Islip, NY, USA), 35 degrees C Thermo-Active Copper NiTi (A-Company/Ormco, Glendora, CA, USA), Rematitan "Lite" (Dentaurum, Pforzheim, Germany), Titanol SE S (Forestadent, Pforzheim, Germany) and Titanal (Lancer, San Marcos, CA, USA) in size 0.016" x 0.022". The chemical composition and surface topography were analyzed by energy dispersive X-ray spectroscopy using an analytical scanning electron microscope (XL30, EDAX SUTW Saphire Detector; Philips, Eindhoven, Netherlands). The transition temperatures were measured by means of differential scanning calorimetry (DSC; Perkin-Elmer Pyris 1, Perkin-Elmer, Fremont, CA, USA) in a range of - 80 degrees C to + 80 degrees C. The mechanical properties and their dependence on temperature were determined by means of 3-point bending tests. The binary archwire materials were characterized by a two-phase structure (NiTi matrix and Ni3Ti4 precipitates). RESULTS: The SEM analyses revealed abradant residues in virtually all archwires, while DSC revealed complex transformation properties. In addition to the martensitic and austenitic transformations, an R-phase transformation was also detected. The bending tests showed pronounced loading and unloading plateaus. The martensitic archwires (Neo Sentalloy F80, 35 degrees C Thermo-Active Copper NiTi) were found to have a lower strength than the martensitic-austenitic (Rematitan "Lite") and the austenitic archwires (Titanol SE S, Titanal). With increasing temperature (in the range from 22 degrees C to 60 degrees C) a linear rise in the plateau forces was recorded. CONCLUSIONS: When assessing the quality of archwires, account should be taken of the surface quality, as it is this that determines corrosion resistance, biocompatibility and friction characteristics. The mechanical properties depend on the initial state; moderate plateau forces and plateau moments can only be achieved with martensitic archwires. In contrast to conventional steel alloys, the strength characteristics are heavily dependent on temperature and need to be known if NiTi archwires are to be used to optimal effect. In addition, the superelastic plateau is used only partially, if at all, when minimum leveling is required.


Asunto(s)
Níquel/análisis , Alambres para Ortodoncia/normas , Titanio/análisis , Rastreo Diferencial de Calorimetría , Microanálisis por Sonda Electrónica , Diseño de Equipo , Humanos , Microscopía Electrónica de Rastreo , Propiedades de Superficie , Resistencia a la Tracción
19.
Nanoscale Res Lett ; 8(1): 363, 2013 Aug 23.
Artículo en Inglés | MEDLINE | ID: mdl-23968229

RESUMEN

We process one-dimensional (1D) NiO nanostructures in anodized alumina templates starting from electrochemically deposited Ni nanotubes (NTs), and characterize their morphology-dependent supercapacitance behavior. The morphology of the 1D NiO nanostructures is controlled by the time of annealing at 450°C. After 25 min of annealing, the NTs start to close but maintain the tubular structure, and after a further 300 min of annealing time, the tubes are completely closed and nanorods (NRs) are formed. We show that the structures obtained are highly promising for supercapacitor applications; the performance of the NiO NT structure is with a specific capacitance of 2,093 F/g, the highest ever obtained for NiO, approaching the theoretical capacitance of this material. A suitable combination of nanocrystalline grain size and the high surface area akin to the tubular structure is responsible for this high performance. In contrast, the NiO NR structure is characterized by lower performance (797 F/g). A further attribute of the proposed structure is its high stability against galvanostatic charging-discharging cycling at high current densities, with almost no alteration to performance after 500 cycles.

20.
Artículo en Inglés | MEDLINE | ID: mdl-23007771

RESUMEN

The suitability for use in pyroelectric detectors of single-crystalline doped and undoped lead indium niobate-lead magnesium niobate-lead titanate was tested and compared with high-quality Mn-doped lead magnesium niobate-lead titanate and standard lithium tantalate. Pyroelectric and dielectric measurements confirmed an increased processing and operating temperature range because of the higher phase transitions of lead indium niobate-lead magnesium niobate-lead titanate. Pyroelectric coefficients of 705 to 770 µC/m(2)K were obtained with doped and undoped lead indium niobate-lead magnesium niobate-lead titanate, which are about 70% to 80% of the pyroelectric coefficient of lead magnesium niobate-lead titanate but 4 times higher than standard lithium tantalate. Manganese doping has been proved as a solution to decrease the dielectric loss of lead magnesium niobate-lead titanate and it also works well for lead indium niobate-lead magnesium niobate-lead titanate. An outstanding specific detectivity D* of about 1.1 · 10(9) cm·Hz(1/2)/W was achieved at a frequency of 2 Hz for Mn-doped lead magnesium niobate-based detectors.

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