A quantitative evaluation model to measure the disassembly difficulty; application of the semi-destructive methods in aviation End-of-Life

Sustainable decommissioning of aircraft with a high content of metallic and non-metallic components is a current challenge in the industry. This process has historically appeared to be economically, environmentally and socially unviable. Literature indicates that, unlike entirely destructive and totally non-destructive techniques, semi-destructive disassembly may bring significant benefits. However, despite their use in a wide variety of applications, there are currently no feasible solutions on how to measure the associated physical difficulties and required efforts without any dependencies on expert views or filling out spreadsheet-like forms. In this paper, a new model is developed to accurately evaluate the disassembly easiness of an airframe quantitatively incorporating both product and process features. Based on a real disassembly of a passenger jet, the cutting and thrust force vectors are selected to evaluate and find the best operation sets. An airliner Horizontal Stabiliser is analysed as a case study. The results indicate that minor drilling, as a hybrid operation, can reduce the disassembly efforts significantly while offering an increased material recovery chance. Such quantitative evaluation can help to: proceed with a viable End-of-Life strategy; and implement newer approaches like automated disassembly by designing better disassembly robots, tool selection and process control.     

THF hydrate crystal growth inhibition with small anionic organic compounds and their synergistic properties with the kinetic hydrate inhibitor poly(N-vinylcaprolactam)

Small, cationic tetraalkylammonium ions (particularly for alkyl=butyl or pentyl) are known to inhibit tetrahydrofuran (THF) and natural gas hydrate crystal growth and have been used as synergists for commercial kinetic hydrate inhibitor polymers (KHIs), such as N-vinylcaprolactam polymers, for a number of years. The ability for small, organic anionic molecules to inhibit (THF) hydrate crystal growth and their potential as KHI synergists in blends with poly(N-vinylcaprolactam) have been investigated. Several series of sodium alkyl carboxylates, sulphates and sulphonates were synthesised. It was found that none of these molecules were capable of inhibiting THF hydrate crystal growth as well as the best tetraalkylammonium salts. Alkyl carboxylates appeared to be more effective as inhibitors than the sulphonates or sulphates. The most effective anionic THF hydrate crystal growth inhibitors had butyl or pentyl groups, with alkyl branching at the tail (i.e. iso- rather than n-isomers) being advantageous. Anionic carboxylate molecules, particularly with isopentyl or isobutyl groups, showed some kinetic inhibition synergy with poly(N-vinylcaprolactam) lowering the onset and catastrophic hydrate formation temperatures in high pressure (78 bar) constant cooling experiments with Structure II hydrates by 1–2 °C when dosed at 2500 ppm compared with using 2500 ppm polymer alone. This synergism was however less than the best tetraalkylammonium salts (alkyl=n-butyl or n-pentyl) at the same test conditions. Sodium butyl sulphonate and sodium 4-methylpentanoate did not prevent hydrate agglomeration with 3.6% brine and decane at 25% water cut in stirred sapphire cells when dosed at 20,000 ppm based on the aqueous phase, whereas 10,000–20,000 ppm active material of several commercially available anti-agglomerants gave fine transportable slurries and no hydrate deposits at the same conditions.     

Using ultrasound to improve the sequential post-synthesis modification method for making mesoporous Y zeolites

Mesoporous Y zeolites were prepared by the sequential chemical dealumination (using chelating agents such as ethylenediaminetetraacetic acid, H₄EDTA, and citric acid aqueous solutions) and alkaline desilication (using sodium hydroxide, NaOH, aqueous solutions) treatments. Specifically, the ultrasound-assisted alkaline treatment (i.e., ultrasonic treatment) was proposed as the alternative to conventional alkaline treatments which are performed under hydrothermal conditions. In comparison with the hydrothermal alkaline treatment, the ultrasonic treatment showed the comparatively enhanced efficiency (with the reduced treatment time, i.e., 5 min vs. 30 min, all with 0.2 mol·L⁻¹ NaOH at 65°C) in treating the dealuminated Y zeolites for creating mesoporosity. For example, after the treatment of a dealuminated zeolite Y (using 0.1 mol·L⁻¹ H₄EDTA at 100°C for 6 h), the ultrasonic treatment produced the mesoporous zeolite Y with the specific external surface area (S_external) of 160 m²·g⁻¹ and mesopore volume (V_meso) of 0.22 cm³·g⁻¹, being slightly higher than that by the conventional method (i.e., S_external = 128 m²·g⁻¹ and V_meso = 0.19 cm³·g⁻¹). The acidic property and catalytic activity (in catalytic cracking of n-octane) of mesoporous Y zeolites obtained by the two methods were comparable. The ultrasonic desilication treatment was found to be generic, also being effective to treat the dealuminated Y zeolites by citric acid. Additionally, the first step of chemical dealumination treatment was crucial to enable the effective creation of mesopores in the parent Y zeolite (with a silicon-to-aluminium ratio, Si/Al= 2.6) regardless of the subsequent alkaline desilication treatment (i.e., ultrasonic or hydrothermal). Therefore, appropriate selection of the condition of the chemical dealumination treatment based on the property of parent zeolites, such as Si/Al ratio and crystallinity, is important for making mesoporous zeolites effectively.     

Synthesis and Characterization of New Cobalt(II)–Pyrazine Coordination Polymer as Precursor for Preparation of Co(II) Oxide Nanoparticles: Surprising Coordination,DFT Calculation and Spectroscopic Studies

The new 2-D cobalt(II) coordination polymer with pyrazine was synthesized surprisingly from reaction of CoCl₂ and tetrapyrido[3,2-a:2′,3′-c:3″,2″-h:2?,3?-j]phenazine (tpphz) in methanol as medium and characterized by means of Fourier transform infrared spectroscopy (FT-IR), UV–Vis spectroscopy and X-ray single crystal analysis. The results showed that coordination polymer consist of cobalt(II) chain with pyrazine-bridged which crystallizes in orthorhombic unit cell (a?=?10.1307, b?=?10.1310, c?=?10.6838 Å) and space group Pban. Density functional theory (DFT) calculations were also done to figure out the electronic structure of the compound from theoretical aspect. The electronic spectrum of coordination polymer was investigated and the DFT/TDDFT procedures were employed to assign the absorption bands. The thermal decomposition of the title compound resulted in formation of cobalt(II) oxide nanoparticles with average size of 50 nm.     

CeO<Subscript>2</Subscript>–WO<Subscript>3</Subscript> Mixed Oxides for the Selective Catalytic Reduction of NO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> by NH<Subscript>3</Subscript> Over a Wide Temperature Range

Abstract  

A series of cerium-tungsten oxide catalysts was prepared by the co-precipitation method and was evaluated for the selective catalytic reduction of NO _x by ammonia (NH₃-SCR) over a wide temperature range. These catalysts were characterized by BET, XRD, XPS and H₂-TPR analyses. The experimental studies demonstrated that, among cerium-tungsten oxides, CeO₂–WO₃ with a Ce/W molar ratio of 3/2 exhibited the best activity toward NH₃-SCR reactions, N₂ selectivity and SO₂ durability over a broad temperature range of 175–500 °C at a space velocity of 47,000 h⁻¹. The strong interaction between Ce and W could be the main factor leading to the high activity of the CeO₂–WO₃ mixed oxide catalyst.     

Catalytic performance of spinel-type Ni-Co Oxides for Oxidation of Carbon Monoxide and Toluene

Topics in Catalysis - This study aims to investigate the catalytic activity of spinel-type oxides (NixCoyO4) for the oxidation of toluene and carbon monoxide at low temperatures. A series of Ni/Co...     

Antibacterial activities and corrosion behavior of novel PEO/nanostructured ZrO2 coating on Mg alloy

Plasma electrolytic oxidation (PEO) was developed as a bond coat for air plasma sprayed (APS) nanostructure ZrO₂ as top coat to enhance the corrosion resistance and antibacterial activity of Mg alloy. Corrosion behavior and antibacterial activities of coated and uncoated samples were assessed by electrochemical tests and agar diffusion method toward Escherichia coli (E. coli) bacterial pathogens, respectively. The lowest corrosion current density and the highest charge transfer resistance, phase angle and impedance modulus were observed for PEO/nano-ZrO₂ coated sample compared with those of PEO coated and bare Mg alloys. Nano-ZrO₂ top coat which has completely sealed PEO bond coat is able to considerably delay aggressive ions transportation towards Mg alloy surface and significantly enhances corrosion resistance of Mg alloy in simulated body fluid (SBF) solution. Moreover, higher antibacterial activity was also observed in PEO/nano-ZrO₂ coating against bacterial strains than that of the PEO coated and bare Mg alloys. This observation was attributed to the presence of ZrO₂ nanoparticles which decelerate E. coli growth as a result of E. coli membranes.     

Effects of Fe substitutions by Ni in La–Ni–O perovskite-type oxides in reforming of methane with CO2 and O2

LaNiO₃ and LaNi_1−xFe_xO₃ (x = 0.2, 0.4, 0.6, 0.8 and 1) perovskites were prepared by the citrate sol–gel method. The prepared compounds were characterized by using thermogravimetric analysis (TGA) and X-ray diffraction (XRD), temperature programmed reduction (TPR), and inductively coupled plasma (ICP) techniques. Specific surface area of the samples was measured by BET method. Morphology study of the prepared catalysts was performed using scanning and transmission electron microscopy (SEM and TEM, respectively). The XRD patterns of fresh catalysts indicated the formation of well-crystallized perovskite structure as the main phase present in the prepared samples. The results showed that the highly homogeneous and pure solids with particle sizes in the range of nanometers were obtained through this synthesis method. TPR analysis revealed that by increasing the degree of substitution (x) the reduction of the prepared samples became difficult. The effects of the partial substitution of Ni by Fe and reaction temperatures at atmospheric pressure were investigated in the combined reforming of methane with CO₂ and O₂ (CRM), after reduction of the samples under hydrogen. LaNiO₃ exhibited high activity and selectivity without coke formation between all of the studied perovskites. Among Fe-substituted catalysts, the following order of activity was observed: LaNiO₃>LaNi_0.4Fe_0.6O₃>LaNi_0.6Fe_0.4O₃ > LaNi_0.8Fe_0.2O₃ > LaNi_0.2Fe_0.8O₃ > LaFeO₃.