Search results for "Pyrolytic carbon"
showing 10 items of 15 documents
Size dependence of the Josephson critical behavior in pyrolytic graphite TEM lamellae
2014
We have studied the transport characteristics of TEM lamellae of different widths obtained from a graphite sample with electrical contacts at the edges of the embedded interfaces. The temperature dependence of the resistance, as well as the current-voltage characteristics, are compatible with the existence of Josephson-coupled superconducting regions. The transition temperature at which the Josephson behavior sets in decreases with a decreasing interface width and vanishes for widths below 200 nm. This interface-size dependence provides an explanation for differences observed in the transport behavior of graphite-based samples with interfaces, and it appears to be related to the influence o…
Tuning the Magnetic Properties of Carbon by Nitrogen Doping of Its Graphene Domains
2015
Here we present the formation of predominantly sp-coordinate carbon with magnetic- and heteroatom-induced structural defects in a graphene lattice by a stoichiometric dehalogenation of perchlorinated (hetero)aromatic precursors [hexachlorobenzene, CCl (HCB), and pentachloropyridine, NCCl (PCP)] with transition metals such as copper in a combustion synthesis. This route allows the build-up of a carbon lattice by a chemistry free of hydrogen and oxygen compared to other pyrolytic approaches and yields either nitrogen-doped or -undoped graphene domains depending on the precursor. The resulting carbon was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM…
Mass spectrometric investigation of polymers: Thermal degradation of truxillic and truxinic polyamides
1975
The thermal degradation mechanism of four isomeric truxillic and truxinic polyamides were investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation reactions were followed directly by this method by detecting the thermal and electron impact-induced fragments. The results obtained have shown that the thermal degradation products are sensibly different for the head-to-head (hh) and head-to-tail (ht) polymers and that the predominant pyrolytic process is the cyclobutane ring cleavage. In the hh isomers, both symmetrical and asymmetrical cyclobutane ring cleavage was detected, while in the ht isomers only symmetrical cleavage occurs; this explains the notice…
Stabilization of MCM-41 by Pyrolytic Carbon Deposition
2000
A new method of surface modification which is effective in stabilizing silica grades of MCM-41 in the presence of water vapor is presented. It is shown by means of XRD, low-temperature nitrogen ads...
Phase Composition and Morphology of Tungsten Oxide Nanoparticles Produced via a Pyrolytic Process
2018
The chemical synthesis is a leading route for the purposeful design of nanomaterials, whereas the tungsten oxides are employed in a variety of special applications. The production of nanomaterials by traditional synthetic methods is still a cumbersome multistep procedure. Here we propose an improved method to produce tungsten oxide nanoparticles via a pyrolytic process. A tungsten-containing precursor was prepared by liquid extraction using n-trioctylamine (C8H17)3N solution in toluene. We have shown that the conditions of thermal treatment of the W-based precursor determine the crystalline structure and nanomorphology of the final product. Monoclinic WO3 nanocrystallites are produced condu…
Superconducting properties of polycrystalline YBCO prepared by a pyrolytic process
1994
Polycrystalline YBCO was prepared by a pyrolytic process starting from citrate and tartrate precursors. The effect of the precursor on the superconducting properties was investigated by means of magnetic measurements using a SQUID magnetometer, a Vibrating-Sample Magnetometer and an a.c. susceptometer. The critical temperature is not affected by the type of precursor (Tc=85 K for both). On the other hand, the precursor plays an important role on the critical current density, which is found to be an order of magnitude higher in the sample obtained from citrates (Jc(77K, H=0)=2.3·104 A/cm2 and 103 A/cm2 for the from-citrate and from-tartrate sample, respectively).
Auto-assembly of nanometer thick, water soluble layers of plasmid DNA complexed with diamines and basic amino acids on graphite: Greatest DNA protect…
2017
Abstract We have investigated the ability of diamines as well as basic amino acids to condense DNA onto highly ordered pyrolytic graphite with minimum damage after re-dissolution in water. Based on a bibliographic survey we briefly summarize DNA binding properties with diamines as compared to basic amino acids. Thus, solutions of DNA complexed with these linkers were drop-cast in order to deposit ultra-thin layers on the surface of HOPG in the absence or presence of Tris buffer. Atomic Force Microscopy analyses showed that, at a fixed ligand-DNA mixing ratio of 16, the mean thickness of the layers can be statistically predicted to lie in the range 0–50 nm with a maximum standard deviation ±…
STRUCTURE AND MAGNETIC PROPERTIES OF COBALT FERRITE PARTICLES PRODUCED BY METHOD OF PYROLYTIC SYNTHESIS
2008
ABSTRACT Magnetic fine particles of cobalt ferrite have been prepared by method of pyrolytic synthesis. X-ray diffraction confirmed the formation of single-phase cobalt ferrite nanoparticles in the range 6–50 nm. The size of the particles varies depending on matrix dispersity and mass content in the organic precursors. A large coercivity observed to be small for smaller single-domain particles due to superparamagnetic behavior.
Multiband light emission and nanoscale chemical analyses of carbonized fumed silica
2018
Fumed silica with a specific area of 295 m2/g was carbonized by successive phenyltrimethoxysilane treatments followed by annealing in inert atmosphere up to 650 °C. Emission, excitation, kinetics, and photo-induced bleaching effects were investigated by steady state and time-resolved photoluminescence spectroscopies. The local chemistry was also studied by infrared transmission spectroscopy. Strong ultraviolet and visible photoluminescence was observed in the samples after the chemical treatments/modifications and thermal annealing. It has been shown that ultraviolet photoluminescence in chemically modified fumed silica is associated with phenyl groups, while near ultraviolet and visible em…
On the pyrolytic decomposition of cadmium carbonate
1996
The pyrolytic decomposition of cadmium carbonate was studied by thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermoanalysis (DTA) and exoemission of electrons (EEE).