Abstract
For the first time, GdBa
2
Cu
3
O
7−
x
nanocomposites were prepared by chemical solution deposition following the ex-situ approach. In particular, ~ 220 nm GdBa
2
Cu
3
O
7−
x
-HfO
2
...(GdBCO-HfO
2
) nanocomposite films were fabricated starting from a colloidal solution of 5 mol% HfO
2
nanoparticles. Hereby, one of the main challenges is to avoid the accumulation of the nanoparticles at the substrate interface during the pyrolysis, which would later prevent the epitaxial nucleation of the GdBCO grains. Therefore, the effect of pyrolysis processing parameters such as heating ramp and temperature on the homogeneity of the nanoparticle distribution has been investigated. By increasing the heating ramp to 300 °C/h and decreasing the final temperature to 300 °C, a more homogenous nanoparticle distribution was achieved. This translates into improved superconducting properties of the grown films reaching critical temperatures (
T
c
) of 94.5 K and self-field critical current densities (
$${J}_{\mathrm{c}}^{\mathrm{sf}}$$
J
c
sf
) at 77 K of 2.1 MA/cm
2
with respect to films pyrolyzed at higher temperatures or lower heating ramps.
Monometallic cerium layered double hydroxides (Ce-LDH) supports were successfully synthesized by a homogeneous alkalization route driven by hexamethylenetetramine (HMT). The formation of the Ce-LDH ...was confirmed and its structural and compositional properties studied by XRD, SEM, XPS, iodometric analyses and TGA. HT-XRD, N
-sorption and XRF analyses revealed that by increasing the calcination temperature from 200 to 800 °C, the Ce-LDH material transforms to ceria (CeO
) in four distinct phases, i.e., the loss of intramolecular water, dehydroxylation, removal of nitrate groups and removal of sulfate groups. When loaded with 2.5 wt% palladium (Pd) and 2.5 wt% nickel (Ni) and calcined at 500 °C, the PdNi-Ce-LDH-derived catalysts strongly outperform the PdNi-CeO
benchmark catalyst in terms of conversion as well as selectivity for the hydrogenolysis of benzyl phenyl ether (BPE), a model compound for the α-O-4 ether linkage in lignin. The PdNi-Ce-LDH catalysts showed full selectivity towards phenol and toluene while the PdNi-CeO
catalysts showed additional oxidation of toluene to benzoic acid. The highest BPE conversion was observed with the PdNi-Ce-LDH catalyst calcined at 600 °C, which could be related to an optimum in morphological and compositional characteristics of the support.
This work discusses the development of an analysis routine for evaluating the nanoparticle distribution in nanocomposite thin films. YBa2Cu3O7−δ (YBCO) nanocomposite films were synthesized via a ...chemical solution deposition approach starting from colloidal YBCO solutions with preformed nanoparticles. The distribution of the nanoparticles and interlayer diffusion are evaluated with X-ray photoelectron spectroscopy (XPS) depth profiling and compared with cross-sectional transmission electron microscopy (TEM) images. It is shown that the combination of both techniques deliver valuable information on the film properties as nanoparticle distribution, film thickness and interlayer diffusion.
The ytterbium aluminum garnet composition YbAG (62.5 mol.% Al
2
O
3
, 37.5 mol.% Yb
2
O
3
) was prepared in the form of glass microspheres by flame synthesis. Precursor powder for flame synthesis ...with high homogeneity was prepared by modified sol–gel Pechini method. XRD pattern of prepared glass microspheres indicated predominantly amorphous nature of the sample. Detailed study of morphology of the microspheres by scanning electron microscopy revealed the presence of a small fraction of partially or fully crystallized microspheres. The high-temperature X-ray powder diffraction analysis (HT XRD) was carried out in the temperature interval 750–1450 °C: The temperature dependence of phase composition was determined. Crystallization of Yb
3
Al
5
O
12
—ytterbium aluminum garnet phase—was observed in the temperature range 900–1200 °C. The DSC analysis with heating rates 2, 4, 6, 8, 10 °C min
−1
in temperature interval 25–1200 °C was performed in N
2
atmosphere to study thermal behavior and crystallization kinetics of prepared glass microspheres. The two exothermic effects at 918 and 939 °C were observed, which were attributed to Yb
3
Al
5
O
12
crystallization. The crystallization kinetics of prepared sample was examined with the use of JMAK model, and the kinetic triplet—frequency factor
A
= (1.8 ± 2.2) 10
+28
min
−1
(for the first peak),
A
= (1.2 ± 1.6) 10
+55
min
−1
(for the second peak), apparent activation energy
E
app
= (6.4 ± 0.1) 10
+02
kJ mol
−1
(for the first peak),
E
app
= (1.3 ± 0.1) 10
+03
kJ mol
−1
(for the second peak) and the Avrami coefficient
m
= 3 (for the first peak) and
m
= 2 (for the second peak)—was determined using RSS,
R
adj
2
, AIC and
W
AIC
criteria.
The Ni-doped Ca
2
Al
2
SiO
7
glass systems were prepared by flame synthesis. Solid-state reaction was used to prepare the powder precursors. The concentration of Ni was 0.5, 1 and 3 mol%. ...Polydisperse systems were prepared with diameters between 5 and 140 μm. Detailed examination of morphology of the glass microbeads by SEM revealed no features indicating the presence of crystalline phases. However, X-ray diffraction analysis showed that the samples GNi0.5 (0.5 mol% of Ni) and GNi1.0 (1.0 mol% of Ni) contained traces of crystalline gehlenite. HT-XRD was used to determine the temperature dependence of phase composition. For all prepared compositions, only one crystalline phase (Ca
2
Al
2
SiO
7
) was observed. DSC measurements in the temperature range 30–1200 °C at five different heating rates were carried out to study the thermal behavior. The DSC curves of all glasses contained one exothermic peak, which was attributed to crystallization of the gehlenite. The maximum of the peak decreased with increasing Ni content in the microspheres. The kinetic parameters (frequency factor
A
, apparent activation energy
E
app
and the Avrami coefficient
m
) of the crystallization were determined using the Johnson–Mehl–Avrami–Kolgomorov model. In case of GNi0.5 and GNi1.0 glasses, the nucleation’s rate had linear temperature dependence, the crystal growth interface is controlled by chemical boundary and the crystal growth is one-dimensional. The rate of nucleation is linear, the crystal interface growth is controlled by diffusion and one-dimensional crystal growth prevails in crystallization of the GNi3.0 (3.0 mol% of Ni).
Lanthanum zirconate (LZO) films from water-based precursors were deposited on Ni-5%W tape by chemical solution deposition. The buffer capacity of these layers includes the prevention of Ni oxidation ...of the substrate and Ni penetration towards the YBCO film which is detrimental for the superconducting properties. X-ray Photoelectron Spectroscopy depth profiling was used to study the barrier efficiency before and after an additional oxygen annealing step, which simulates the thermal treatment for YBCO thin film synthesis. Measurements revealed that the thermal treatment in presence of oxygen could severely increase Ni diffusion. Nonetheless it was shown that from the water-based precursors' buffer layers with sufficient barrier capacity towards Ni penetration could be synthesized if the layers meet a certain critical thickness and density.
This paper compares different coating methods (in situ solid combustion, hybrid deposition, secondary growth on seed, suspension, double deposition of wet impregnation and suspension) to deposit ...Ce0.2Zr0.8O2 mixed oxides on cordierite substrates, for use as a three way catalyst. Among them, the double deposition was proven to be the most efficient one. The coated sample shows a BET (Brunauer–Emmett–Teller) surface area of 25 m2/g, combined with a dense and crack free surface. The catalyst with a layer of MnO2–NiO–Co3O4 mixed oxides on top of the Ce0.2Zr0.8O2/cordierite substrate prepared by this method exhibits good activity for the treatment of CO, NO and C3H6 in exhaust gases (CO conversion of 100% at 250 °C, C3H6 conversion of 100% at 400 °C and NO conversion of 40% at 400 °C).
In today’s research, smart textiles is an established topic in both electronics and the textile fields. The concept of producing microelectronics directly on a textile substrate is not a mere idea ...anymore and several research institutes are working on its realisation. Microelectronics like organic field effect transistor (OFET) can be manufactured with a layered architecture. The production techniques used for this purpose can also be applied on textile substrates. Besides gate, active and contact layers, the isolating or dielectric layer is of high importance in the OFET architecture. Therefore, generating a high quality dielectric layer that is of low roughness and insulating at the same time is one of the fundamental requirements in building microelectronics on textile surfaces. To evaluate its potential, we have studied polyimide as a dielectric layer, dip-coated onto copper-coated polyester filaments. Accordingly, the copper-coated polyester filament was dip-coated from a polyimide solution with two different solvents, 1-methyl-2-pyrrolidone (NMP) and dimethylformaldehyde. A variety of dip-coating speeds, solution concentrations and solvent-solute combinations have been tested. Their effect on the quality of the layer was analysed through microscopy, leak current measurements and atomic force microscopy (AFM). Polyimide dip-coating with polyimide resin dissolved in NMP at a concentration of 15w% in combination with a dip-coating speed of 50 mm/min led to the best results in electrical insulation and roughness. By optimising the dielectric layer’s properties, the way is paved for applying the subsequent semi-conductive layer. In further research, we will be working with the organic semiconductor material TIPS-Pentacene
The idea of wearable electronics automatically leads to the concept of integrating electronic functions on textile substrates. Since this substrate type implies certain challenges in comparison with ...their rigid electronic companions, it is of utmost importance to investigate the application of materials for generating the electronic functions on the textile substrate. Only when interaction of materials and textile substrate is fully understood, the electronic function can be generated on the textile without changing the textile’s properties, being flexible or stretchable. This research deals with the optimization of the dielectric layer in a fibrous organic field effect transistor (OFET). A transistor can act as an electrical switch in a circuit. In this work, the polyimide layer was dip-coated on a copper-coated polyester filament. After thoroughly investigating the process conditions, best results with minimal thickness and roughness at full insulation could be achieved at a dip-coating speed of 50 mm/min. The polyimide solution was optimal at 15w% and the choice for the solvent NMP was made. In this paper, details on the pre-treatment methods, choice of solvent and dip-coating speed and their effect on layer morphology and thickness, electrical properties and roughness are reported. Results show that the use of polyimide as a dielectric layer in the architecture of a fibrous OFET is promising. Further research deals with the application of the semiconductor layer within the mentioned architecture, to finally build an OFET on a filament for application in smart textiles.
IMPORTANCE: Dexamethasone initiated after the first week of life reduces the rate of death or bronchopulmonary dysplasia (BPD) but may cause long-term adverse effects in very preterm infants. ...Hydrocortisone is increasingly used as an alternative, but evidence supporting its efficacy and safety is lacking. OBJECTIVE: To assess the effect of hydrocortisone initiated between 7 and 14 days after birth on death or BPD in very preterm infants. DESIGN, SETTING, AND PARTICIPANTS: Double-blind, placebo-controlled randomized trial conducted in 19 neonatal intensive care units in the Netherlands and Belgium from November 15, 2011, to December 23, 2016, among preterm infants with a gestational age of less than 30 weeks and/or birth weight of less than 1250 g who were ventilator dependent between 7 and 14 days of life, with follow-up to hospital discharge ending December 12, 2017. INTERVENTIONS: Infants were randomly assigned to receive a 22-day course of systemic hydrocortisone (cumulative dose, 72.5 mg/kg) (n = 182) or placebo (n = 190). MAIN OUTCOMES AND MEASURES: The primary outcome was a composite of death or BPD assessed at 36 weeks’ postmenstrual age. Twenty-nine secondary outcomes were analyzed up to hospital discharge, including death and BPD at 36 weeks’ postmenstrual age. RESULTS: Among 372 patients randomized (mean gestational age, 26 weeks; 55% male), 371 completed the trial; parents withdrew consent for 1 child treated with hydrocortisone. Death or BPD occurred in 128 of 181 infants (70.7%) randomized to hydrocortisone and in 140 of 190 infants (73.7%) randomized to placebo (adjusted risk difference, −3.6% 95% CI, −12.7% to 5.4%; adjusted odds ratio, 0.87 95% CI, 0.54-1.38; P = .54). Of 29 secondary outcomes, 8 showed significant differences, including death at 36 weeks’ postmenstrual age (15.5% with hydrocortisone vs 23.7% with placebo; risk difference, −8.2% 95% CI, −16.2% to −0.1%; odds ratio, 0.59 95% CI, 0.35-0.995; P = .048). Twenty-one outcomes showed nonsignificant differences, including BPD (55.2% with hydrocortisone vs 50.0% with placebo; risk difference, 5.2% 95% CI, −4.9% to 15.2%; odds ratio, 1.24 95% CI, 0.82-1.86; P = .31). Hyperglycemia requiring insulin therapy was the only adverse effect reported more often in the hydrocortisone group (18.2%) than in the placebo group (7.9%). CONCLUSIONS AND RELEVANCE: Among mechanically ventilated very preterm infants, administration of hydrocortisone between 7 and 14 days after birth, compared with placebo, did not improve the composite outcome of death or BPD at 36 weeks’ postmenstrual age. These findings do not support the use of hydrocortisone for this indication. TRIAL REGISTRATION: Netherlands National Trial Register Identifier: NTR2768
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