33 research outputs found
Electrochemical Formation of Second Generation TiO2 Nanotubes on Ti13Nb13Zr Alloy for Biomedical Applications
The aim of this study was to obtain the second generation TiO2 nanotubes on the Ti13Nb13Zr alloy. Anodic
oxidation of the alloy under study was carried out in 1 M (NH4)2SO4 electrolyte under voltage–time conditions of
20 V for 120 min. The morphological parameters of the obtained nanotubes of second generation such as the length
(L), internal (Di) and outer (Do) diameter of nanotube were determined. It was found that the anodic oxidation
of the Ti13Nb13Zr alloy conducted under proposed conditions allowed to obtain the single-walled nanotubes of the
following geometrical parameters: the internal diameter 61 nm, outer diameter 103 nm, and the length 3.9 μm.
The total surface area of the single-walled nanotubes was equal to 4.1 μm2, and the specific surface area per cm2
(As) was estimated to be 15.6 cm2/cm2. Formation mechanism, structure and optimal morphological parameters
of the obtained single-walled nanotubes on the Ti13Nb13Zr alloy have been discussed in detail
Preparation and characterization of nitinol bone staples for cranio-maxillofacial surgery
The aim of this work was to form NiTi and TiNiCo body temperature activated and superelastic staples for
clinical joining of mandible and face bone fractures. The alloys were obtained by VIM technique. Hot and
cold processing was applied to obtain wires of required diameters. The martensitic transformation was
studied by DSC, XRD, and TEM. The shape memory effects were measured by a bend and free recovery
ASTM F2082-06 test. The superelasticity was recorded in the tension stress-strain and by the three-point
bending cycles in an instrument equipped with a Hottinger force transducer and LVDT. Excellent superelastic
behavior of TiNiCo wires was obtained after cold working and annealing at 400-500 C. The body
temperature activated shape memory staples were applied for fixation of mandibular condyle fractures. In
experiments on the skull models, fixation of the facial fractures by using shape memory and superelastic
staples were compared. The superelastic staples were used in osteosynthesis of zygomatico-maxillo-orbital
fractures
Microstructure, phase transformations, and properties of hot-extruded Ni-rich NiTi shape memory alloy
Processing of NiTi shape memory alloys strongly influences their microstructure, phase transformations,
mechanical, and shape memory properties. Hot forging, hot swaging, or hot rolling are efficient techniques
for obtaining the desired shape, but during multiple operations the material must be heated and worked in
the temperature range from 700 to 900 C. During these processes, intense oxidation takes place. In order
to reduce it, the hot-pack working is applied. The hot extrusion is more effective for reduction of ingot,
billet, and rod diameters than hot forging, hot swaging, or hot rolling. Also, during hot extrusion the
material surface undergoes considerably less oxidation. In the present work, results of the characterization
by differential scanning calorimetry, low-temperature x-ray powder diffraction, and three-point bending
and free recovery ASTM F2082-06 tests of the samples after hot direct extrusion and heat treatment are
presented. The obtained alloy after hot direct extrusion exhibits desired shape memory effect. The phase
transformations during cooling and heating cycle occur with the presence of the R phase. The range of the
characteristic temperatures for the obtained material gives possibility for further medical applications.
After annealing at 400 and 500 C, the characteristic temperatures shift to higher values
Structure and Properties of NiTi Shape Memory Alloy after Cold Rolling in Martensitic State
Due to unique features, like shape memory effects and superelasticity, NiTi alloys with nearly equiatomic
composition are used in various branches of industry. Application of severe plastic deformation can drastically
change properties of the materials. In the present paper the Ni50:4Ti49:6 alloy after cold rolling in the martensitic
state and further annealed is studied. Phase transformations were studied using X-ray diffraction and differential
scanning calorimetry measurements. Microstructure was examined using transmission electron microscopy and
electron backscattering diffraction methods. Mechanical properties of obtained alloys has been studied using
Vickers microhardness tests. Based on the performed measurements it can be seen that in studied alloys two steps
B2 B190 phase transitions occurred. Performed plastic deformation influences course of phase transitions
and phases composition. Due to the reduction of grain size microhardness of the studied material is increasing
with increase of deformation degree
NiTi Shape Memory Marformed Alloy Studied by Electron Beam Precession TEM Orientation Mapping Method.
Severe plastic deformation by cold-rolling in martensitic state was applied to Ni50:4Ti49:6 shape memory
alloy. Received materials with 17, 20, 25, and 35% deformation were further annealed at 450 C for 15 min.
After such treatment hardness of this alloy increased significantly reaching 365 HV0.5 for highest deformation
degree. Calorimetric studies revealed two-stage and two-step character of martensitic transformation occurring in
all specimens. Nanocrystalline structure with average grain size 53, 34, 28, and 24 nm was obtained. In material
with 35% of deformation amorphous regions containing a nuclei of B2 parental phase with average size of 5 nm
were observed. To determine the crystallographic orientation of observed nanograins and for better phase analysis,
electron beam precession transmission electron microscopy orientation mapping was performer[…
Effect of Nanoparticles Surface Charge on the Arabidopsis thaliana (L.) Roots Development and Their Movement into the Root Cells and Protoplasts
Increasing usage of gold nanoparticles (AuNPs) in different industrial areas inevitably
leads to their release into the environment. Thus, living organisms, including plants, may be exposed
to a direct contact with nanoparticles (NPs). Despite the growing amount of research on this topic,
our knowledge about NPs uptake by plants and their influence on different developmental processes
is still insufficient. The first physical barrier for NPs penetration to the plant body is a cell wall
which protects cytoplasm from external factors and environmental stresses. The absence of a cell wall
may facilitate the internalization of various particles including NPs. Our studies have shown that
AuNPs, independently of their surface charge, did not cross the cell wall of Arabidopsis thaliana (L.)
roots. However, the research carried out with using light and transmission electron microscope
revealed that AuNPs with different surface charge caused diverse changes in the root’s histology
and ultrastructure. Therefore, we verified whether this is only the wall which protects cells against
particles penetration and for this purpose we used protoplasts culture. It has been shown that plasma
membrane (PM) is not a barrier for positively charged (+) AuNPs and negatively charged () AuNPs,
which passage to the cell
Novel piezoelectric paper based on SbSI nanowires
A novel piezoelectric paper based on
antimony sulfoiodide (SbSI) nanowires is reported.
The composite of tough sonochemically produced
SbSI nanowires (with lateral dimensions 10–100 nm
and length up to several micrometers) with very
flexible cellulose leads to applicable, elastic material
suitable to use in fabrication of, for example, piezoelectric
nanogenerators. For mechanical energy harvesting,
cellulose/SbSI nanocomposite may be used.
Due to its high values of electromechanical coefficient
(k33 = 0.9) and piezoelectric coefficient
(d33 = 1 9 10-9 C/N), SbSI is a very attractive
material for such devices. The preliminary investigations
of a simple cellulose/SbSI nanogenerator for
shock pressure (p = 3 MPa) and sound excitation
(f = 175 Hz, Lp = 90 dB) allowed to determine its
open circuit voltage 2.5 V and 24 mV, respectively.
For a load resistance equal to source impedance
(ZS = 2.90(11) MX), maximum output power density
(PL = 41.5 nW/cm3 for 0.05-mm-thick sheet of this
composite) of the cellulose/SbSI nanogenerator was
observed. Cellulose/SbSI piezoelectric paper may also
be useful to construct gas nanosensors and actuators
Precession electron diffraction studies of SrxBa1-xNb2O6 and CaxBa1-xNb2O6 single crystals
Crystal structures of two single crystals SrxBa1xNb2O6 and CaxBa1xNb2O6 have been reinvestigated using
automated electron diffraction tomography method with beam precession. 3D reciprocal space has been reconstructed
based on recorded tilt series. For both samples the crystal structure was refined and the tetragonal
symmetry with space group P4bm was confirmed. The three dimensional reciprocal space allowed to observe and
to study satellite reflections in both materials
Fate of neutral-charged gold nanoparticles in the roots of the Hordeum vulgare L. cultivar Karat
Nanoparticles (NPs) have a significant impact on the environment and living organisms. The influence of NPs on plants is intensively studied and most of the data indicate that NPs can penetrate into plants. The studies presented here were performed on the roots of Hordeum vulgare L. seedlings using neutral-charge gold nanoparticles (AuNPs) of different sizes. In contrast to the majority of the published data, the results presented here showed that during the culture period, AuNPs: 1/did not enter the root regardless of their size and concentration, 2/that are applied directly into the cells of a root do not move into neighbouring cells. The results that were obtained indicate that in order to extend our knowledge about the mechanisms of the interactions between NPs and plants, further studies including, among others, on different species and a variety of growth conditions are needed
Characterization of long-term corros ion performance of ti15mo alloyin saline solution
The Ti15Mo alloy has been studied towards long-term corrosion performance in saline solution at 37° C using electrochemical impedance spectroscopy. The physical and chemical characterization of the material were also investigated. The as-received Ti15Mo alloy exhibits a single β-phase structure. The thickness of single-layer structured oxide presented on its surface is ~4 nm. Impedance measurements revealed that the Ti15Mo alloy is characterized by spontaneous passivation in the solution containing chloride ions and formation of a double-layer structured oxide composed of a dense interlayer being the barrier layer against corrosion and porous outer layer. The thi ckness of this oxide layer, estimated based on the impedance data increases up to ~6 nm during 78 days of exposure. The obs erved fall in value of the log|Z|f = 0.01 Hz indicates a decrease in pitting corrosion resistance of Ti15Mo alloy in saline solution along with the immersion time. The detailed EIS study on the kinetics and mechanism of corrosion process and the capacitive behavior of the Ti15Mo electrode | passive layer | saline solution system was based on the concept of equivalent electrical circuit with respect to the physical meaning of the applied circuit elements. Potentiodynamic studies up to 9 V vs. SCE and SEM analysis show no presence of pitting corrosion what indicates that the Ti15Mo alloy is promising biomaterial to long-term medical applications