Hydrogen-free Atmosphere Research Articles

Selective Deoxygenation of Sludge Palm Oil into Diesel Range Fuel over Mn-Mo Supported on Activated Carbon Catalyst

Originating from deoxygenation (DO) technology, green diesel was innovated in order to act as a substitute for biodiesel, which contains unstable fatty acid alkyl ester owing to the existence of oxygenated species. Green diesel was manufactured following a process of catalytic DO of sludge palm oil (SPO). An engineered Mn(0.5%)-Mo(0.5%)/AC catalyst was employed in a hydrogen-free atmosphere. The influence of Manganese (Mn) species (0.1–1 wt.%) on DO reactivity and the dissemination of the product were examined. The Mn(0.5%)-Mo(0.5%)/AC formulation gave rise to a superior harvest of approximately 89% liquid hydrocarbons; a higher proportion of diesel fraction selectivity n-(C15+C17) was obtained in the region of 93%. Where acid and basic active sites were present on the Mn(0.5%)-Mo(0.5%)/AC catalyst, decarboxylation and decarbonylation reaction mechanisms of SPO to DO were enhanced. Evidence of the high degree of stability of the Mn(0.5%)-Mo(0.5%)/AC catalyst during five continuous runs was presented, which, in mild reaction conditions, gave rise to a consistent hydrocarbon harvest of >72% and >94% selectivity for n-(C15+C17).

Effective catalytic deoxygenation of palm fatty acid distillate for green diesel production under hydrogen-free atmosphere over bimetallic catalyst CoMo supported on activated carbon

Palm fatty acid distillate (PFAD) is considered as an inedible and renewable feedstock for the production of green diesel. In the current study, green diesel was successfully synthesised via catalytic deoxygenation of PFAD in an environment free of H2 using a mesoporous activated carbon (AC) supported CoMo catalyst with various molybdenum (Mo) concentrations (5–20 wt%). Based on the study results, bimetallic catalyst Co10Mo10/AC formulation exhibited excellent catalytic performance with 92% hydrocarbon components (C8-C20) yield and 89% selectivity for n-(C15 + C17) with a total acid number of 24 mg KOH mg−1. Based on a comparison study with various supports (AC, γ-Al2O3, TiO2), the AC-supported CoMo catalyst showed higher deoxygenation activity than both Co10Mo10/γ-Al2O3 and Co10Mo10/TiO2 owing to the super acid-base sites as a result of synergism between the CoMo and AC support. The Co10Mo10/AC catalyst demonstrated excellent stability during the study as it maintained the hydrocarbon components yield and selectivity of n-(C15 + C17) >80% until the sixth run.

Synthesis and capacitance properties of N-doped porous carbon/NixCoyOz/carbon micro–nanotubes composites using coal-based polyaniline as a carbon and nitrogen source

Using coal-based polyaniline as a carbon and nitrogen source, N-doped porous carbon (NPC)/nickel cobalt oxides (NixCoyOz)/carbon micro–nanotubes (CMNT) composites possessing rich nanoscale meso–macropores, spinel NiCo2O4 sheets and multi-walled CMNT are successfully synthesized by the first pyrolysis and the second wet oxidation process. Therein, CMNT owning a diameter of 10–200 nm and a length of several micrometers is grown by a two-stage furnace process in a hydrogen-free atmosphere, using nickel acetate as a growth catalyst precursor. CMNT exhibits polymorphic features, including most curved tubes, a few vertical tubes, some bamboo-like tubes and some Chinese-sugar-gourd-skewer-like tubes, resulting from the diversity and low hydrogen content of gaseous cracking products from coal-based polyaniline. Carbon in CMNT mainly exists in the graphitic state while carbon in NPC mainly presents in the amorphous state. Nitrogen in CMNT mainly exists in the form of graphitic N while nitrogen in NPC (0.89 wt% in composites) mainly presents in the form of pyrrolic N (74.4 at.%) and oxidized N (25.6 at.%). The intercalated Ni and Co impurity in NPC and CMNT are transformed to most NiCo2O4 and a few NiO. The BET specific surface area and average pore width of composites are 169.3 m2/g and 8.4 nm. CMNT incorporation obviously improves capacitance properties of NPC/NixCoyOz/CMNT composites. The composites demonstrate a higher specific capacitance of 598.4 F/g at 1 A/g, and a good cycling stability retaining a high capacity of 190.1 F/g (81.1% retention) at 5 A/g after 5000 charge–discharge cycles. It is attributed to the nitrogen incorporation of porous carbon, high conductivity and large specific surface area of CMNT, and high electrochemical activity of NixCoyOz, especially, the synergistic effects of NPC, CMNT and NixCoyOz. This study has developed a polygeneration process for coal pyrolysis, which also enables the combined utilization of coal pyrolysis products.

Influence of Hydrogen on the Ion Nitriding of Steels

We present the results of experimental investigations of the contact durability of specimens of different steels after ion nitriding in hydrogen and hydrogen-free atmospheres tested in the І-20 lubricant. The detrimental influence of hydrogen on the contact durability of steels in rolling friction is demonstrated.

Catalytic cracking of wax esters extracted from Euglena gracilis for hydrocarbon fuel production

Wax esters (WEs) synthesized by Euglena gracilis are potential sources for alternative fuels because of their high productivity, recent success in mass cultivation, and low energy consumption in extraction. In this study, deoxygenation of Euglena WE and conversion to hydrocarbons in a catalytic cracking process under a hydrogen-free atmosphere was investigated using a residue fluid catalytic cracking equilibrium catalyst with enhanced hydrogen-transfer activity. The deoxygenation of Euglena WE proceeded more rapidly with higher H2O selectivity than that of saturated triglycerides. This is because initial β-elimination of WEs produces saturated fatty acids and higher olefins; the higher olefins rapidly release hydrogen species during cracking, cyclization and aromatization, and the hydrogen species accelerate hydrodeoxygenation of the saturated fatty acids. Furthermore, the cracking of Euglena WE produced large amounts of paraffins and olefins instead of aromatics. Therefore, Euglena WE was confirmed to be a preferable feedstock for the catalytic cracking process for hydrocarbon fuel production.

Low-Cycle Fatigue of Steels After Ion Nitriding in Hydrogen-Free Atmospheres

We present the results of investigation of low-cycle fatigue in bending for different types of steel after ion nitriding in hydrogen-free saturating atmospheres. The recommendations concerning the field of applicability of this technology of surface hardening in the process of operation are given. We make a conclusion that the procedure of ionic hardening in hydrogen-free atmospheres makes it possible to change the physicomechanical properties of the surface layers in broad ranges and substantially increase the low-cycle fatigue strength of structural steels. The maximum durability is attained by optimizing the parameters of the process of diffusion saturation.

Effective Catalytic Deoxygenation of Waste Cooking Oil over Nanorods Activated Carbon Supported CaO

Under nitrogen atmosphere, waste cooking oil (WCO) was deoxygenated in semi-batch experiments by using the nanorods of phosphate-activated carbon, which is derived from walnut shell and promoted by CaO as catalyst at 350 °C. The deoxygenation reaction showed high activity (> 48% hydrocarbon yield) and high selectivity towards decarboxylation/decarbonylation (deCOx) reactions via exclusive formation of green diesel C15 fraction (> 60%). The high activity and high selectivity were attributed to the good physicochemical characteristics of the catalyst, including improved metal dispersion, high surface area and high basic properties. Overall, this study demonstrates CaO/AC catalytic deoxygenation as a promising approach to produce liquid green diesel C15 from WCO under hydrogen-free atmosphere.

Properties of InGaN/GaN heterostructures obtained using growth interruption under various conditions

Conversion of the near-surface regions of InGaN into GaN during growth interruption has been studied. It has been established that the process exhibits saturation in time, develops at a depth below 2 nm, and proceeds in a similar way in the presence and absence of hydrogen, although hydrogen supply significantly accelerates the conversion process. InGaN/GaN heterostructures obtained with interruption of growth exhibit an additional photoluminescence line with a longer wavelength as compared to that for an otherwise analogous continuous InGaN layer. It is established that growth interruption in a hydrogen-free atmosphere is more favorable for obtaining light-emitting structures for the green spectral range.

Influence of the annealing atmosphere on solution based zinc oxide thin film transistors

ABSTRACTZinc oxide layers with a thickness of less than 10 nanometers have been synthesized from an aqueous solution for the application as active layer in thin film transistors. They have been conditioned by applying different oxidizing and reducing atmospheres during an annealing process at a temperature of 125°C. It is shown that the charge carrier mobility and threshold voltage is strongly influenced by the annealing atmosphere. Samples annealed in 10% forming gas (H2 in N2 - reducing atmosphere) show the highest field-effect-mobility of 0.6 cm2V-1s-1, but no saturation of the drain current, due to a high free carrier concentration. Samples treated under oxygen (strongest oxidizing atmosphere) show significantly lower mobilities. Subsequently, the samples have been exposed to synthetic air, with varying exposure times. Samples which have been annealed under hydrogen atmospheres show a pronounced decay of the drain current if exposed to synthetic air, whereas all samples conditioned under hydrogen-free atmospheres are significantly more stable under synthetic air. This enhanced sensitivity against oxygen after hydrogen treatment is attributed to residual hydrogen content in the sample that supports the formation of OH-groups which act as electron acceptors.

Nickel and Nickel-Based Nanoalloy Thin Films from Alcohol-Assisted Chemical Vapor Deposition

The growth of nickel and nickel-based alloys was investigated using the pulsed-spray evaporation (PSE) CVD process in hydrogen-free atmosphere. This process relies on the reactivity of ethanol, which was investigated using mass spectrometry. In fact, the dehydrogenation of ethanol to form acetaldehyde is identified as the reaction pathway that provides hydrogen atoms necessary to desorb acetylacetonate ligand of the precursor. This global reaction leads to the formation of metallic nickel film either in the hexagonal (hcp) lattice at low temperature or in the cubic (fcc) one at temperatures higher than 240 °C. In conditions where the fcc−Ni phase is deposited, the PSE−CVD process enables the deposition of Ni−Cu alloy thin films with fully controlled composition, whereas Ni−Ag forms polycrystalline silver, in addition to an amorphous phase containing silver and nickel. The synthesis of Ni−Co alloy thin films was performed under conditions where the hcp−Ni phase was obtained, providing for the first time a route toward deposition of nickel-rich hcp−Ni−Co.

Low-temperature synthesis of multiwalled carbon nanotubes by graphite antenna CVD in a hydrogen-free atmosphere

Multiwalled carbon nanotubes (MWCNTs) were synthesized at 390 °C in a hydrogen-free atmosphere by graphite antenna chemical vapor deposition, which provides carbon radicals by the etching of the antenna itself in a He- or Ar-based noble gas plasma. An increase in the number of defects in the graphite layers of the CNTs was observed with increasing hydrogen partial pressure. The results of X-ray photoelectron spectroscopy analysis suggested that these defects were caused by the transformation from an sp 2 to an sp 3 structure in the graphite layers of CNTs due to hydrogen radicals.

Mixed Conduction in BaCe0.8Pr0.2O3- Ceramic

BaCe0.8Pr0.2O3- ceramic was synthesized by high temperature solid-state reaction. The structural characteristics and the phase purity of the crystal were determined using powder X-ray diffraction analysis. By using the methods of AC impedance spectroscopy, gas concentration cell and electrochemical pumping of hydrogen, the conductivity and ionic transport number of BaCe0.8Pr0.2O3- were measured, and the electrical conduction behavior of the material was investigated in different gases in the temperature range of 500-900 C. The results indicate that the material was of a single perovskite-type orthorhombic phase. From 500 C to 900 C, electronic-hole conduction was dominant in dry and wet oxygen, air or nitrogen, and the total conductivity of the material increased slightly with increasing oxygen partial pressure in the oxygen partial pressure range studied. Ionic conduction was dominant in wet hydrogen, and the total conductivity was about one or two orders of magnitude higher than that in hydrogen-free atmosphere (oxygen, air or nitrogen).

Protonic and electronic conductivities of terbium doped strontium cerates

Electronic and protonic conductivities of Tb doped SrCeO 3 were measured in a hydrogen containing and hydrogen-free atmosphere of the same oxygen partial pressure in 500–900 °C. In a H 2 containing atmosphere, the material exhibits mixed electronic and proton-conductivity and, for SrCe 0.95Tb 0.05O 3-δ, the proton transfer number increases with decreasing temperature, from about 0.4 at 900 °C to about 0.8 at 500 °C. The total conductivity for SrCe 0.95Tb 0.05O 3-δ decreases from about 3 × 10 − 3 S/cm in the reducing atmosphere to 4 × 10 − 5 S/cm in air at 900 °C with an activation energy respectively of 39 kJ/mol and 76 kJ/mol for protonic and n-type electronic conduction. Results of XRD analysis show a decrease in the lattice volume of the SrCe 1- x Tb x O 3-δ with increasing Tb concentration. SrCe 1- x Tb x O 3-δ exhibits negligible proton-conductivity with x smaller than 0.005. At 800 °C under a reducing atmosphere, SrCe 1-xTb xO 3-δ, with x > 0.005, are mixed electronic and proton conductors with a maximum proton-conductivity of about 3 × 10 − 3 S/cm at x = 0.025 and proton transfer number of about 0.7 for x in the range of 0.005–0.125.

Effect of Solvent on the Growth of Co and Co2C Using Pulsed-Spray Evaporation Chemical Vapor Deposition

Cobalt and cobalt carbide films were obtained using chemical vapor deposition (CVD) at low pressure in a hydrogen-free atmosphere at temperatures below 300 °C. Although the growth over bare glass was enabled, the use of a 5 nm nickel seed layer improves the morphology and eliminates the incubation time. The pulsed-spray evaporation using alcohol solutions of cobalt acetylacetonate as a liquid feedstock allows the growth of metallic cobalt or cobalt carbide, depending on the choice of the alcohol and of the deposition temperature. The growth of Co2C was obtained, for the first time with CVD, using an ethanol precursor solution at temperatures in the range of 205–230 °C, whereas the deposition of high-quality metallic crystalline cobalt is attained with an n-propanol precursor solution at substrate temperatures above 250 °C. The obtained metallic films reach a near-bulk electrical resistivity for thicknesses above 300 nm.

Catalytically enhanced H 2-free CVD of transition metals using commercially available precursors

The deposition of metals using thermal CVD in a hydrogen-free atmosphere was investigated starting from nontoxic metalorganic precursors. A remarkably simple process, which relies on the chemical reduction by alcohols, allows the deposition of high-quality films of a variety of metals and alloys. The growth characteristics of metal films are investigated as a function of temperature, and their performance is discussed in terms of electrical resistivity. Near-bulk resistivities were obtained for Ni, Co, Cu, and Ag, while Fe presents a 37-fold higher resistivity than the bulk because of the poor packing of crystallites. In this work, the deposition conditions for the growth of single-phase cubic or hexagonal nickel were determined.

Synthesis of double-walled carbon nanotubes from coal in hydrogen-free atmosphere

Double-walled carbon nanotubes (DWNTs) were synthesized from coal in large quantity by arc-discharge method in hydrogen-free atmosphere, which were systematically examined using scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The results show that the as-synthesized DWNTs have an outer diameter of 1.0–5.0 nm with an interlayer spacing in the tube walls of ca. 0.41 nm. The possible mechanism involved in the formation process of DWNTs is proposed and discussed in term of the unique chemical composition of coal and the process parameters adopted in the study.

The formation of helium lines in the spectrum of COM J1740-5340

The Hei λ5876 Å absorption line recently discovered in the spectrum of the companion to the millisecond pulsar PSR J1740–5340 is tentatively attributed to electron impact excitations due to the irradiation of its atmosphere by γ-rays emitted by the pulsar's magnetosphere. Numerical calculations, similar to those carried out previously for type Ib SNe, indicate that a pulsar beam with photon energies ~1 MeV gives rise to a λ5876 Å line of the observed strength if the beam's spin-down conversion efficiency approaches 1%. However, a significant difficulty for the proposed mechanism is the strength of the singlet line at λ6678 Å. Compared to the corresponding triplets, singlet lines are weak because of the loss of excitation when photons emitted in the series ionize hydrogen atoms, an effect absent in the hydrogen-free atmospheres of type Ib SNe.

High-Quality Double-Walled Carbon Nanotube Super Bundles Grown in a Hydrogen-Free Atmosphere

High-quality double-walled carbon nanotube (DWNT) super bundles were selectively grown above a bowl-like cathode by arc discharge in a hydrogen-free atmosphere. These DWNTs can resist high-temperature (up to 720 °C) oxidation in air without additional annealing even after acid treatment, which is due to an in-situ defect-healing effect of the bowl-like cathode and the absence of reactive gases during arc discharge. Selective formation of DWNTs is ascribed to the increased presence of carbon clusters in the enlarged hot plasma region inside the cathode and optimized composition of the catalysts.

Radical Modification of Gate Oxide by Lateral Gettering of Electroactive Centers

An approach to radically modifying gate dielectric by laterally gettering electroactive defects (centers) is suggested. Gettering of the ionized centers is accomplished through intentionally creating structure defects in the surface layers of the side oxide that are adjacent to the periphery of the gate oxide. The process was carried out at low temperatures, e.g., during postmetallization annealing in a hydrogen-free atmosphere. The structure defects in the side oxide capture excessive hydrogen, which otherwise produces ionized donors in the gate oxide layer. If the gate size is comparable to the hydrogen diffusion length (5–10 μm), ionized acceptor centers of concentration no more than 1011 cm–2 dominate in the gate oxide after annealing. This is apparently related to the minimization of excessive hydrogen content in the gate oxide of structures with small lateral dimensions.

Experimental investigation of the influence of modes of nitriding on the damping ability of 45 steel

By using numerical methods, for specimens of 45 steel subjected to various modes of nitriding in a hydrogen-free atmosphere, we determine the parameters of the process of nitriding guaranteeing the maximum possible level of their damping ability. The results of testing control specimens of 45 steel subjected to the optimal procedure of nitriding revealed practically complete coincidence between the numerical and experimental values of the decrement of vibrations whose level was higher than for nonnitrided specimens by a factor of 3.4.