Formation Mechanism of Preferential Flow Paths and Seepage Characteristics of a Novel Growable Pile for Heap Leaching of Rare Earth

In the traditional heap leaching of rare earth minerals, the top of the rare earth pile is covered with leaching liquid. This creates trouble for vegetation restoration carried out timely on the top of the pile. In order to solve this trouble, a novel pile structure into which leaching liquid is laterally injected is proposed for heap leaching of rare earth. In this study, a laboratory test is carried out to study the formation and distribution of preferential flow paths for the rare earth pile under a horizontal liquid injection condition. Furthermore, numerical simulations based on a dual-permeability model are conducted to investigate the influence of the preferential flow paths on the seepage characteristics in the rare earth pile. The results show that, under the horizontal liquid injection condition, the fine particles of the rare earth move away from the liquid injection end and also toward the lower part of the pile. The migration of the fine particles results in the formation and connection of macropore, thereby generating preferential flow paths in the rare earth pile. The preferential flow paths are mainly distributed in the lower part of the pile near the liquid injection end. This causes the fluid in the lower part of the pile to seep faster significantly than that in the upper part. Within the region where the preferential flow paths develop, the seepage in the early stage of the horizontal liquid injection is dominated by preferential flow. The preferential flow is more significant at the locations farther away from the liquid injection end.

Synthesis of Carbon Nanotubes via Liquid Injection Chemical Vapour Deposition as a Vector for the Chemical Recycling of Waste Composite Carbon Sources

For every three people on the planet there is approximately two Tonne (Te) of available plastic waste. We show that carbon recovery from polystyrene (PS) plastic is enhanced by the co-addition to solvents to grow carbon nanotubes (CNTs) by liquid injection chemical vapour deposition. Polystyrene was loaded up to 4 wt% in toluene and heated to 780 °C in the presence of a ferrocene catalyst and a hydrogen/argon carrier gas in a 1:19 ratio. High resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Raman spectroscopy were used to identify multi-walled carbon nanotubes (MWCNTs). The PS addition in the range from 0 to 4 wt% showed improved quality and CNT homogeneity; Raman “Graphitic/Defective” (G/D) values increased from 1.9 to 2.3; mean CNT diameters increased from 43.0 to 49.2 nm; and maximum CNT yield increased from 11.3% to 14.2%. Since both the CNT diameters and the percentage yield increased with respect to polystyrene addition, we conclude that carbon from the PS contributes to the carbon within the MWCNTs. The electrical contact resistance of acid washed Bucky papers produced from each loading, ranged from 2.2 to 4.4 Ohm, with no direct correlation to PS loading. Due to this narrow range, the materials with different loading were mixed to create six wires of an Ethernet cable and tested using iPerf to give uplink and downlink speeds of ~99.5 Mbps, comparable to Cu wire of identical dimension (~99.5 Mbps). The lifecycle assessment (LCA) of CNT wire production was compared to copper wire production for the use case in a Boeing 747-400 over the lifespan of the craft. Due to their lightweight nature the CNT wires decreased the CO2 footprint by 21 kTonne (kTe) over the aircraft lifespan.

Optimizing Bladder Resin Transfer Molding Process to Manufacture Complex, Thin-Ply Thermoplastic Tubular Composite Structures: An Experimental Case Study

The bladder molding process is primarily used in sporting applications but mostly with prepregs. Bladder-Assisted Resin Transfer Molding (B-RTM) presents the tremendous potential to automate and mass produce the complex hollow-composite profiles. Thin-ply, non-crimp fabrics (NCFs) provide excellent mechanical, fracture toughness, and vibration damping properties on top of the weight saving it offers to a final product. However, these fiber architectures are difficult to inject due to the resistance they provide for the polymer flow using the liquid injection process. Therefore, it is mandatory to optimize the process parameters to reduce the time for injection and simultaneously achieve better consolidation. This work presents a first, detailed, experimental case study to successfully inject a low-permeability, thin-ply, complex, thermoplastic tubular structure, and the effect of process parameters, boundary conditions, the associated manufacturing challenges, and proposed solutions are deliberated in this paper.

Negative-ion field desorption revitalized by using liquid injection field desorption/ionization-mass spectrometry on recent instrumentation

Field ionization (FI), field desorption (FD), and liquid injection field desorption/ionization (LIFDI) provide soft positive ionization of gaseous (FI) or condensed phase analytes (FD and LIFDI). In contrast to the well-established positive-ion mode, negative-ion FI or FD have remained rare exceptions. LIFDI provides sample deposition under inert conditions, i.e., the exclusion of atmospheric oxygen and water. Thus, negative-ion LIFDI could potentially be applied to highly sensitive anionic compounds like catalytically active transition metal complexes. This work explores the potential of negative-ion mode using modern mass spectrometers in combination with an LIFDI source and presents first results of the application of negative-ion LIFDI-MS. Experiments were performed on two orthogonal-acceleration time-of-flight (oaTOF) instruments, a JEOL AccuTOF GCx and a Waters Micromass Q-TOF Premier equipped with LIFDI sources from Linden CMS. The examples presented include four ionic liquids (ILs), i.e., N-butyl-3-methylpyridinium dicyanamide, 1-butyl-3-methylimidazolium tricyanomethide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, and trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluorophosphate), 3-(trifluoromethyl)-phenol, dichloromethane, iodine, polyethylene glycol diacid, perfluorononanoic acid, anionic surfactants, a tetraphosphazene silanol-silanolate, and two bis(catecholato)silanes. Volatile samples were delivered as vapors via the sample transfer capillary of the LIFDI probe or via a reservoir inlet. Condensed phase samples were applied to the emitter as dilute solutions via the sample transfer capillary. The compounds either yielded ions corresponding to their intact anions, A−, or the [M–H]− species formed upon deprotonation. This study describes the instrumental setups and the operational parameters for robust operation along with a discussion of the negative-ion LIFDI spectra of a variety of compounds.

Gas flow control in rocket engines

In the new conditions of application of launch vehicle boosters, space tugs, etc., modern rocket engines often do not satisfy the current stringent requirements. This calls for fundamental research into processes in rocket engines for improving their efficiency. In this regard, for the past 5 years, the Department of Thermogas Dynamics of Power Plants of the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine has conducted research on gas flow control in rocket engines to improve their efficiency and functionality. Mechanisms of flow perturbation in the nozzle of a rocket engine by liquid injection and a solid obstacle were investigated. A mathematical model of supersonic flow perturbation by local liquid injection was refined, and new solutions for increasing the energy release rate of the liquid were developed. A numerical simulation of a gas flow perturbed by a solid obstacle in the nozzle of a rocket engine made it possible to verify the known (mostly experimental) results and to reveal new perturbation features. In particular, a significant increase in the efficiency of flow perturbation by an obstacle in the transonic region was shown up, and some dependences involving the distribution of the perturbed pressure on the nozzle wall, which had been considered universal, were refined. The possibility of increasing the efficiency of use of the generator gas picked downstream of the turbine of a liquid-propellant rocket engine was investigated, and the advantages of a new scheme of gas injection into the supersonic part of the nozzle, which provides both nozzle wall cooling by the generator gas and the production of lateral control forces, were substantiated. A new concept of rocket engine thrust vector control was developed: a combination of a mechanical and a gas-dynamic system. It was shown that such a thrust vector control system allows one to increase the efficiency and reliability of the space rocket stage flight control system. A new liquid-propellant rocket engine scheme was developed to control both the thrust amount and the thrust vector direction in all planes of rocket stage flight stabilization. New approaches to the process organization in auxiliary elements of rocket engines on the basis of detonation propellant combustion were developed to increase the rocket engine performance.