Abstract: Nb-1 wt% Zr polycrystalline and single crystalline samples were submitted to annealing,
at pressure of 2.5 x 10-8 Torr and subsequently annealed in an oxygen atmosphere for three hours, in
a temperature of 1170 K in oxygen at partial pressure of 5 x 10-5 Torr. Internal friction
measurements as a function of temperature were performed between 300 K and 650 K, using a
torsion pendulum inverted Kê-type operating in a frequency oscillation in the hertz bandwidth.
Three internal friction peaks, which were assigned as Nb-O, Zr-O and Nb-N peaks were observed in
oxidized single crystal sample and the relaxation parameters of the three peaks were obtained.
Abstract: Measurements of the H-induced damping peak in Zr-based multi-component metallic
glasses, with different tendency to quasicrystal formation, are added to previous reviews of the
properties of this damping peak in metallic glasses, and also compared to Ti-Zr-Ni quasicrystals.
The results, mainly discussed in terms of a Snoek-type relaxation mechanism for both structure
types, indicate a negative correlation between the degree of icosahedral order and the temperature
of the damping peak, so that improved damping properties of hydrogen-absorbing bulk metallic
glasses can apparently be expected from stronger deviations from icosahedral short-range order.
Abstract: Hydrogenated Zr-Cu-base metallic glasses (MGs) are the potential high-damping and
high-strength materials. On the other hand, the knowledge on the material parameters which govern
the peak temperature, Tp, and the peak height, Q-1
p, of the hydrogen internal friction peak (HIFP)
remains poor. In order to pursue this issue, the hydrogen concentration dependence of Tp and Q-1
the Zr-Cu-base MGs were investigated in the point of view of the hydrogen induced structural
relaxation (HISR). It is found that the Tp vs. CH data and the Q-1
p vs. CH data are well fitted by the
relationships of Tp = Tp exp(-CH/τH) +Tp,0 and Qp
-1 ∝ ln(CH/τH), respectively, for various
Zr-Cu-base MGs including bulk MGs, Zr55Cu30Al10Ni5 and Zr60Cu30Al10. That is, the observed
relationship between Tp and CH is mainly governed by HISR. It is suggested that Tp,0 in Zr-Cu-base
MGs is the highest among various MGs resulting in the highest Tp in Zr-Cu-base MGs. In other
words, the control of Tp,0 is the key issue to find the high-Tp MGs.
Abstract: The hydrogen-induced internal friction and mechanical strength of the Ti-rich
Ti34Zr11Cu47Ni8 and (Ti34Zr11Cu47Ni8)98Si2 hydrogenated glassy alloys have been investigated. It is
found that the tensile strength is more than 0.8 GPa at room temperature when the hydrogen content is
below about 20 at% for both alloys. The frequency dependence of peak temperature of the
hydrogen-induced internal friction of (Ti34Zr11Cu47Ni8)98Si2-17.3 at%H hydrogenated glassy alloys
has been clarified. Activation energy and pre-exponential factor are estimated to be 0.35 eV and
1.3x10-12, respectively. Compared with these values with those of Zr40Cu49Al10Si1 hydrogenated
glassy alloys which show an internal friction peak around 300 K at about 300 Hz, it is found that the
activation energy is much smaller than that of the latter although the pre-exponential factor is almost
the same. Considering their similar composition and different component (Al), it is suggested that the
component Al of the latter glassy alloys is effective for the higher activation energy which results in
the increase of the peak temperature.
Abstract: We have subjected Zr59Cu20Al10Ni8Ti3 glassy sample to internal friction thermal cycle
(IFTC) measurements under various conditions involving changes in heating/cooling rate, strain
amplitude and frequency. Additional low temperature internal friction peaks (ALTIFP) were found
to occur with the characteristic low temperature internal friction peak (CLTIFP) observed for some
glassy alloys. The ALTIFP were enhanced on heating and reduced on cooling. Their strength
increase following the number of IFTC can be related to a stress concentration in some zones of the
glassy structure, which is abruptly relaxed by the viscous flow creating interfaces in the glassy
structure. These interfaces are likely to be formed between atomic clusters. The growth of the
ALTIFP increases significantly the whole IF level (IFL) from 10-4 to 10-2 enhancing the damping
capacity of the glassy sample.
Abstract: In a hydrogen-doped metallic glass, there appear low-temperature and high-temperature
internal friction peaks respectively associated with a point-defect relaxation and the crystallization.
The high-temperature-side slope of low-temperature peak and also the low-temperature-side slope
of high-temperature peak enhance the background internal friction near the room temperature. A
hydrogen-doped Mg-base metallic glass was proposed as a high-damping material to be used near
and somewhat above the room temperature. Stability of the high damping was also checked.
Abstract: High damping materials exhibiting a loss factor higher than 10-2 are generally considered
as polymer or metallic materials. But, it will be interesting to consider ferroelectric or ferrimagnetic
ceramics, in which internal friction can be due to the motion of ferroelectric or magnetic domains.
High level of internal friction can be obtained in these ceramics in a given temperature range. In the
case of ferroelectric ceramics, hard ferroelectrics, such as BaTiO3 or PZT, can show some
relaxation peaks below the Curie temperature due the motion of domain walls and the interaction
between the domain walls and the oxygen vacancies or cationic vacancies.
In the case of ferrimagnetic ceramics, some anelastic manifestations due to the ferrimagnetic
domain walls appear below the Curie Temperature TC. These peaks are linked to the interaction of
domain walls with cation vacancies or cation interstitials or the lattice. Above the Curie
temperature, a relaxation mechanism due to the exchange of cations Mn3+ and their vacancies on
octahedral sites should occur.
Abstract: In this paper, we review the damping mechanisms in oxide materials, such as the
short-range jump of oxygen vacancies and cation vacancies, movement of domain walls, and grain
boundary sliding. Some examples in doped ZrO2, La2CuO4+δ, La2Mo2O9 and other oxide materials
are briefly discussed, in which the damping capacity can reach as high as 30%. These oxides could
be possibly applied as high damping materials either in the form of bulk components, or as
additives in composites, or as hard damping coatings. In the last two potential applications, the high
hardness and strength as well as high damping capacity of the oxides are simultaneously exploited,
which cannot be realized by the usual high-damping metals and alloys.
Abstract: The interest in the use of thermal barrier ceramic coatings as damping treatments has recently arisen
since they were shown to provide sufficient additional damping. Ceramic coatings can be applied
mainly by either Air Plasma Spraying (APS) or Electron Beam - Physical Vapour Deposition (EBPVD).
APS was used to deposit the specimens studied here. Previous research has shown that it is
possible to enhance their damping effectiveness by tailoring the deposition parameters.
This paper presents further work aimed at improving their damping effectiveness significantly by
introducing a second material in the ceramic coating; thus creating a composite system. This paper
covers the experimental findings of impregnating a ceramic damping coating with a number of
commercially available polymeric materials. The most promising case of a type of Polyurethane
provided over 40% improvement and was selected for further tests at various temperatures, ranging
from -40 to 150 C.
Furthermore, the damping and stiffness of ceramic coatings present amplitude-dependent behaviour
which was also taken into consideration when evaluating the composite system. Finally, the paper
concludes with a discussion of these promising findings as well as planned research into
understanding the physical mechanisms dissipating energy in this composite material.