Experimental constraints on fluid-rock reactions during incipient serpentinization of harzburgite
Klein, Frieder
2014-10-20
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15 records were found.
Studies have been undertaken to utilise the possible
potential of the rodlike, helical structures associated with
polyglutamates and polyisocyanates for piezoelectric (PE) and
nonlinear optical (second harmonic generation (SHG))
applications.
Various techniques have been employed to form
samples/films of these polymers containing oriented helices
whose bulk structures are non-centrosymmetric, (an important
criterium for the aforementioned applications).
Owing to the poor yields obtained for certain
intermediates in the synthetic stages of these polymers, only
poly('S-benzyl-L-glutamate) (PBzLG) and poly(n-
hexylisocyanate) (PHIC) were available for subsequent
studies.
Piezoelectric work was limited to hydrostatic
measurements (d3h) made on electrically poled, composite
(guest host), polymer samples. Phase separation was common in
all t...
The pyroelectric, dielectric and DC resistive properties of Sb and Cr-doped ceramics with a base composition of Pb(Mg1/3Nb2/3)0.025(Zr0.825Ti0.175)0.975O3 have been studied. Sb doping has been shown to produce a linear reduction in Curie temperature (TC=−22z+294 °C) with concentration (z) and to give an increase in pyroelectric coefficient from 250 to 310 μCm−2 K−1 for z increasing from 0 to 3 at.%. It also produces first a reduction and then an increase in both dielectric constant and loss, so that the 33 Hz pyroelectric figures of merit (FOM's) are as follows: FV peaks at 3.8×10−2 m2 C−1 and FD peaks at 1.2×10−5 Pa−1/2. The resistivity is increased substantially from 1.1×1011 to ca 6×1011 Ωm with 1 at.% Sb, thereafter changing little. The behaviour has been explained in terms of Sb acting as a donor ion, reducing oxygen vacancy conce...
The single-layer thickness of Pb(Zr0.3Ti0.7)O3(PZT 30/70) thin films made by the sol-gel process is often restricted by the appearance of cracks when a single layer is thicker than 100 nm. Making a film with 1μm thick needs more than 10 times coating cycles, which is sometimes unacceptable. In this study, a sol modified with an additive was used for the preparation of thick PZT films. The thickness of the films depends upon the rotation rate. Up to 700 nm crack-free single layers could be obtained. The deposited films crystallised as the perovskite structure on platinum-buffered silicon by heating at 550°C. The porosity of the thick films was a function of the single layer thickness. A dense PZT film with a single layer 140 nm thick was found to have a very high pyroelectric coefficient (p=2.36×10− 4CK− 1m− 2) and figure of merit (1.88...
Properties of a new type of pyroelectric ceramic structure containing a layer of known porosity laminated between two dense layers, to form a functionally gradient material (FGM), are reported. The combination of theoretical models for pyroelectric, dielectric, and thermal properties gave a model for the pyroelectric voltage figure of merit (FV) in good agreement with experiment, which had shown a 20% improvement for an introduced central layer porosity of 27%. Preliminary pyroelectric responsivity measurements on FGM infrared detectors indicated an even better improvement. It is postulated that this is due to the porous layer acting as a thermal barrier in the structure.
Piezoforce microscopy (PFM) has been used to determine the domain structure of lead zirconate titanate (PZT) (30/70) on an indium tin oxide (ITO)/glass substrate with a TiO2 boundary layer. The PZT nucleates into the perovskite form in a random crystallographic manner, which leads to a random domain structure in the final film. Using PFM it has been possible to visualize the domain structure of the PZT and determine that the domain structure has features as fine as 8 nm herringbone patterns. The possible impact of these structures for future devices utilizing nanoscale features of PZT and especially FeRAM developments is highlighted.
The following paper describes a design of experiments investigation of the deep reactive of pillar structures on a silicon wafer. The etched wafers would subsequently be used as masters for the fabrication of nickel mould inserts for microinjection moulding. Undercuts occur when the pillar base has a smaller cross-section than the apex of the pillar. They therefore affect tolerances of the subsequent nickel mould, its strength and its de-mouldability from the silicon form. The response measured in these experiments was the degree of undercut of micro-scale (10 μm x 10 μm x 40 μm, 5 μm x 5 μm x 40 μm and 2 μm x 2 μm x 40 μm) The literature suggests that gas pressure, platen power, gas flow rate, phase switching times and mask size can all affect the degree of undercut. After examination of this literature, and of manufacturers guideline...
Ta-doped lead-free 0.94NBT-0.06BT-xTa (x=0.0–1.0%) ceramics were synthesized by a conventional solid-state route. XRD shows that the compositions are at a morphotropic phase boundary where rhombohedral and tetragonal phases coexist. The depolarization temperature (Td) shifted to lower temperature with the increase of Ta content. The pyroelectric coefficient (p) of doped ceramics greatly enhanced compared with undoped material and reached a maximum of 7.14×10−4 C m−2 °C−1 at room temperature (RT) and 146.1×10−4 C m−2 °C−1 at Td at x=0.2%. The figure of merits, Fi and Fv, also showed a great improvement from 1.12×10−10 m v−1 and 0.021 m2 C−1 at x=0.0 to 2.55×10−10 m v−1 and 0.033 m2 C−1 at x=0.2% at RT. Furthermore, Fi and Fv show the huge improvement to 52.2×10−10 m v−1 and 0.48×10−10 m v−1 respectively at Td at x=0.2%. FC shows a value...
La and Ta co-doped Lead-free 0.94NBT-0.06BT ceramics were synthesized by a conventional solid-state route. The compositions remain at a morphotropic phase boundary. The depolarization temperature (Td) decreased with increasing doping contents. The room temperature (RT) pyroelectric coefficient (p) was highly enhanced compared with undoped material (3.15 × 10−4 C m−2 °C−1) and reached 12.9 × 10−4 C m−2 °C−1, whereas, at Td, 58.6 × 10−4 C m−2 °C−1 could be obtained rather than 23.9 × 10−4 C m−2 °C−1 for undoped materials. The pyroelectric figure of merits, Fi and Fv, also showed a huge improvement from 1.12 × 10−10 m v−1 and 0.021 m2 C−1 of undoped material to 4.61 × 10−10 m v−1 and 0.078 m2 C−1 of doped materials at RT, and to 20.94 × 10−10 m v−1 and 0.28 × 10−10 m2.C−1 at Td. RT FC values are ∼2.40, 2.46, and 2.57 (×10−9 C cm−2 °C−1) a...
Lead-free 0.94NBT-0.06BT-xLa ceramics at x = 0.0–1.0 (%) were synthesized by a conventional solid-state route. XRD shows that the compositions are at a morphotropic phase boundary where rhombohedral and tetragonal phases coexist. With increasing La3+ content pyroelectric coefficient (p) and figures of merits greatly increase; however, the depolarization temperature (Td) decreases. p is 7.24 × 10−4C m−2 °C−1 at RT at x = 0.5% and 105.4 × 10−4C.m−2 °C−1 at Td at x = 0.2%. Fi and Fv show improvements at RT from 1.12 (x = 0%) to 2.65 (x10 −10 m v−1) (x = 0.5%) and from 0.021 to 0.048 (m2.C−1) respectively. Fi and Fv show a huge increase to 37.6 × 10−10 m v−1 and 0.56 m2 C−1 respectively at Td at x = 0.2%. FC shows values of 2.10, 2.89, and 2.98 (x10−9C cm−2 °C−1) at RT at 33, 100 and 1000 (Hz) respectively. Giant pyroelectric properties ma...
Lead-free 0.94Na0.5Bi0.5TiO3–0.06Ba1+xTiO3 (NBT–0.06B1+xT) ceramics (0.0 ≤ x ≤ 0.03) were synthesized by a conventional solid-state reaction process. X-ray diffraction shows that the compositions are at the morphotropic phase boundary where rhombohedral and tetragonal phase coexist. Grain size slightly changes with the increase of Ba2+ content and reaches the minimum at x = 0.02. The depolarization temperature (Td) decreases with the extra Ba2+content but the lowest Td was obtained at x = 0.01–0.02. The pyroelectric coefficient (p) was measured as a function of Ba2+ content, and increased from 2.90 × 10−4 to 3.54 × 10−4 C m−2 °C−1, and from 55.3 × 10−4 to 740.7 × 10−4 C m−2 °C−1 for x = 0.00 and 0.02 at RT, and depolarization temperature (Td) respectively. The pyroelectric coefficient (p) shows a large increase with rising the temperat...
