The preparation of biodiesel from fatty materials HDO provides a very constructive idea to solve the global clean energy problem. The application of catalytic technology to convert oils into green ...liquid hydrocarbon fuel has great potential for industrial application. The main problem with the development of green diesel technology is the limited number of available non-food sources of fatty acid triglycerides. Also the researchers have made remarkable achievements in the field of catalyst, the stability of the catalyst is insufficient and the selectivity of large molecules of direct alkanes is low. These defects hinder the large-scale resource development of biodiesel. In current paper the potential of hydrodeoxygenation (HDO) of fatty materials and model esters was explored by enhancing the synergy of platinum and tin by using heterometallic (PPh4)3 Pt (SnCl3)5 complex. Heterometallic (PPh4)3 Pt (SnCl3)5 complex provides in its structure platinum and tin atoms linked by a metal–metal bond that causes the originality of catalytic performance. The performance of bimetallic Pt-Sn/Al2O3 catalyst, which is characterized by the Sn/Pt molar ratio of 5/1, has been studied at hydrogen pressure 50 atm and temperature 400–480 °C. HDO reaction of a number of fatty materials has been shown to proceed with the highest ever yield of direct hydrocarbons derived from alkoxy and acyl groups of the initial ester. Also it was investigated a performance in HDO reaction of mixture containing rapeseed oil oleic acid and water that simulate cooked oil that may be a prospective soure for green hydrocarbons in megalopolises. A structural studies of the catalyst showed that its high selectivity in HDO reaction of fatty materials provided by two important factors: impregnated particles size and formation of intermettallic species of PtSn3±σ. Finally, catalysts sustained activity and stability were tested during five turns of 24 h each.
•Hydrodeoxygenation of rapeseed oil to alkanes selectivity reaches up to 90%.•Original precursor (PPh4)3Pt(SnCl3)5 was used for catalyst synthesis.•Intermetallic alloy PtSn3 clusters formation causes high selectivity of the catalyst.•Different active sites for hydrodeoxygenation and decarboxylation/decarbonylation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The effect of ultrasound treatment of expanded graphite (EG) on structure and tribological behavior of PTFE-EG composites filled with 5 mass % of EG is studied. It is found that sonicated EG (EGS) ...increases the friction coefficient of PTFE composite compared to that of the composite filled with the original EG (EGO). Filling with EG allows to reduce the wear rate of PTFE up to a factor of ≈700 to Kw≈6×10−7mm3/Nm depending on the friction conditions. At high sliding velocity causing high frictional heating, the wear rate of PTFE-EGS composite is several times higher than that of PTFE-EGO owing to reduced thermooxidative stability of both EGS and PTFE-EGS composite, whereas at friction regimes with small frictional heating the wear rates of the two composites are similar.
It is also found that the wear rates reduce with the increasing content of iron carboxylates in the friction layer of the composites, which evolve from interaction of the counterface steel with the products of PTFE tribochemical degradation. The counterface steel is transferred onto the friction surface of the composite specimen in the form of spherical particles of micrometer-nanometer size range according to SEM and electron probe analysis. Chemical bonding of the fine steel particles to the tribochemically modified macromolecules of PTFE reinforces the running film and improves the wear resistance of the composites. Both the content of transferred iron and the wear resistance of PTFE-EG composites increase significantly with the increase in the relative humidity of the ambient air.
EG filler aggregates delaminate at friction into thinner platelets of nanographite which may accumulate in the friction surface layer of the composites. Accumulation of the filler is more expressed in highly wear resistant composites and has an additional effect on reduction of the wear rate.
•Sonication of EG improves strength and increases friction of PTFE-EG composite.•Sonication reduces EG resistance to thermal oxidation and thermal stability of PTFE-EG composite.•The wear rate of PTFE-EG composite is unaffected by EG sonication except for high velocity regimes.•Wear of PTFE-EG composite on steel correlates with content of iron carboxylates in the running film.•Content of iron carboxylates and wear resistance grow with the rise in ambient air humidity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper presents the conceptual design of a high-voltage pulser intended to generate 30-T magnetic fields for magneto-inertial fusion experiments at the OMEGA facility. The pulser uses a custom ...capacitor bank and two externally triggered spark gaps to drive a multiturn coil. This new high-voltage pulser is capable of storing 10 times more energy than the previous system, using a higher charge voltage (from 20 to 30 kV) and a larger capacitance (from 1 to5μF). Circuit simulations show that this pulser can deliver 100 kA into a 60-nH,14−mΩcoil with a rise time of1μs. For a coil with two turns with an average coil diameter of 7.8 mm, this current translates into a 32-T peak magnetic field at coil center. This is a factor of 3 increase in the peak magnetic field compared to the present generator magnetic field capabilities.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM, UPUK
Effect of molybdenum disulfide dispersity and friction test conditions on wear rate of its 1%-filled PTFE-based composites is studied. It is found that under certain test conditions the wear rates of ...the composites filled with sub micro- or nanosized filler are similar to reported values for the PTFE composites filled with 20mass%–30vol% of microsized MoS2. It is attributed to accumulation of the highly dispersed filler particles producing discrete MoS2 coatings over parts of the friction surface.
Results of IR-spectroscopic study of the friction layer polymer show that PTFE macromolecules undergo tribochemical processes of hydrolytic degradation comprising main chain scission, defluorination, hydrogenation and hydroxylation presumably catalyzed by highly dispersed MoS2 at higher friction temperature, which may additionally enhance the composites׳ wear resistance.
•PTFE filled with 1% of ultrafine MoS2 may show low wear of 20%-filled microcomposite.•It is caused by MoS2 accumulation and spreading, enhanced by adhesion and softening.•PTFE resin undergoes tribochemical hydrolytic degradation in low wear rate composites.•It is probably catalyzed by MoS2 and facilitates the evolution of wear-resistant surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Uniaxial spin-1 magnets with tensor interactions have been studied in the absence of external magnetic field. The model with the most general form of interactions for the uniaxial symmetry has been ...investigated. Conditions for the implementation of only two quadrupole phases are considered: the phase with a quadrupole ordering along the lattice symmetry axis and the phase with ordering in the plane normal to the lattice symmetry axis. It has been shown that components of the quadrupole order parameter as a function of the single-ion anisotropy constant at low temperatures has “hysteresis” character. An analytical expression for the remagnetization energy per lattice site has been obtained.
•Uniaxial magnet with unity spin are studied in absence of external magnetic field.•The influence of the single-ion anisotropy on the behaviour of the qudrupole ordering is investigated in detail.•The new type of “hysteresis” in such a magnet has been discovered.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A self-organization of eight structurally and magnetically nonequivalent positions of manganese Mn
2+
ions in the unit cell of a single crystal of the lithium–gallium Li
0.5
Ga
2.5
O
4
spinel is ...demonstrated. These ions are self-distributed over such positions and minima of the crystal field potential. The self-organized structures form during the crystal growth. Such a self-distribution of manganese ions is observed and studied in the electron paramagnetic resonance (EPR) spectra.
The building block of the linear transformer driver pulser, known as a brick, can be thought of as the smallest, independent unit from which the entire pulser is built. In a “standard” brick ...configuration, two capacitors and a spark-gap switch are connected in series and are oil insulated. Such a brick could be assembled, for example, from two 80-nF, 100-kV capacitors and a 200-kV spark-gap switch. A single brick in this configuration is capable of generating a current pulse with up to 50 kA of peak current and a rise time on the order of 100 ns, after the capacitors have been discharged at a combined output voltage of 200 kV (twice the bipolar charge voltage). By contrast, in a “dry” brick configuration, the two capacitors are placed in parallel and a multigap, multichannel “ball” switch follows them in series. The dry brick is epoxy insulated, and its slightly different configuration allows it to have a peak output current of up to 100 kA, after being discharged at a total output voltage of 100 kV (equal to the unipolar charge voltage). In this paper, we present how these two different brick topologies, either oil insulated (standard) or epoxy insulated (dry), affect a pulser’s output parameters, where the pulser has been constructed by connecting the outputs ofNbricks together in parallel. We find that in many cases, the use of a dry brick configuration results in more current being delivered to the load. We also find that if the time to peak current is not a critical parameter for the experiment, then the lower charging voltage across the switch and the absence of insulating oil make the dry brick an excellent alternative to the standard brick, especially for smaller research laboratories with limited maintenance staff.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM, UPUK
The axial quadrupole phase of uniaxial spin-1 magnet in an external magnetic field has been investigated. The case of magnetic system with the most general form of single‐ion anisotropy and ...anisotropic biquadratic exchange interaction is considered. It is shown that the relative magnetization in the molecular field approximation does not depend on temperature and linearly increases with external magnetic field. Two branches of the spin excitation spectrum are determined. The boundary between the axial quadrupole and angular phases is defined by the condition for softening of the spectrum. The critical temperature of the corresponding phase transition considerably depends on the anisotropy constants of the biquadratic exchange interaction.
•Quadrupole phase of uniaxial spin-1 magnet in external magnetic field are studied.•Influence of the anisotropic biquadratic exchange interaction is examined.•It is shown that the relative magnetization does not depend on temperature.•Two branches of the spin excitation spectrum are determined.•Dependence of critical temperature from anisotropy constants are built.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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