Designing low-carbon MgO–Al2O3–La2O3–C refractories with balanced performance for ladle furnaces

In order to achieve high-quality and stable production of special steel, the performance of low-carbon MgO-C refractories needs to be further optimized. For this purpose, low-carbon MgO–Al₂O₃–La₂O₃–C refractories with enhanced thermal shock resistance and slag resistance were designed and successfully prepared by introducing Al₂O₃ as a reinforcer and La₂O₃ as a modifier. The results showed that the refractory samples with additives show better overall performance than those without additives. When 10 wt% of Al₂O₃ and La₂O₃ were added, the oxidation resistance, thermal shock resistance and slag resistance of the refractory samples coked at 1400 °C are increased by 13.57%, 17.75% and 43.09%, respectively. The analysis found that this can be mainly attributed to the formation of MgAl₂O₄, Mg₂SiO₄, and 2CaO·4La₂O₃·6SiO₂ and the consequent volume expansion effect and intergranular phase enhancement effect. Therefore, a low-cost and enforceable reinforcement strategy for low-carbon MgO-C refractories is proposed, which is expected to be applied in steelmaking.     

Preparation of hierarchical WO3 dendrites and their applications in NO2 sensing

Hierarchical WO₃ dendrites were synthesized via low-cost and environmental-friendly solvothermal strategy. Characterization results indicated that WO₃ dendrites were composed of several multi-directional dendritic nanosheets. To further understand the formation of WO₃ dendrites, time-dependent experiments were carried out and formation mechanism was investigated. Since such dendritic structures rarely occurred in the field of gas sensing, the synthesized WO₃ dendrites were subjected to detailed NO₂ sensing tests. Results demonstrated that WO₃ dendrites based sensors had low detection limit (200 ppb) and fast response and recovery (7 s, 12 s to 5 ppm NO₂). Moreover, the sensor was also highly sensitive, selective and stable at low optimal operating temperature of 140 °C.     

High pressure EIGA preparation and 3D printing capability of Ti—6Al—4V powder

Ti—6Al—4V alloy powder was processed by electrode induction melting gas atomization (EIGA) at high gas pressure (5.5–7.0 MPa). The effects of atomizing gas pressure on the powder characteristics and the microstructure, along with the mechanical properties of the as-fabricated block by laser melting deposition (LMD), were investigated. The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400 μm, and the median powder size (d₅₀) decreases with increasing gas pressure. The powders with a size fraction of 100–150 μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability. The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%–0.20%. Specimens fabricated by LMD are mainly composed of α+β grains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength (UTS) and yield strength of approximately 1100 and 1000 MPa, respectively. Furthermore, the atomized powders have a favorable 3D printing capability, and the mechanical properties of Ti—6Al—4V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.     

Effects of Sn doping on the manufacturing,performance and carbon deposition of Ni/ScSZ cells in solid oxide fuel cells

This work demonstrates the effect of tin (Sn) doping on the manufacturing, electrochemical performance, and carbon deposition in dry biogas-fuelled solid oxide fuel cells (SOFCs). Sn doping via blending in technique alters the rheology of tape casting slurry and increases the Ni/ScSZ anode porosity. In contrast to the undoped Ni/ScSZ cells, where open-circuit voltage (OCV) drops in biogas, Sn–Ni/ScSZ SOFC OCV increases by 3%. The maximum power densities in biogas are 0.116, 0.211, 0.263, and 0.314 W/cm² for undoped Ni/ScSZ, undoped Ni/ScSZ with 3 wt% pore former, Sn–Ni/ScSZ and Sn–NiScSZ with 1 wt% pore former, respectively. Sn–Ni/ScSZ reduces the effect of the drop in the maximum power densities by 26%–36% with the fuel switch. A 1.28–2.24-fold higher amount of carbon is detected on the Sn–Ni/ScSZ samples despite the better electrochemical performance, which may reflect an enhanced methane decomposition reaction.     

Transportation of powders using a linear motor device

The theory of linear motors has been formulated for both magnetic and non-magnetic reaction plates and criteria established to assess their performance. The predominant mechanism involved in the transportation of ferromagnetic powders cannot be the same as that in a motor device, because basic calculations show that the induced currents in the particles at 50 Hz are small. Instead, the ferromagnetic particles seem to follow the movement of the travelling magnetic field itself.A study of the phenomena associated with the transportation of powders using linear motor devices has been commenced in a SERC project at Loughborough University of Technology. This paper illustrates the motion of the particles along a linear motor device and also reviews the experimental work done previously, especially that associated with powder cleaning devices. Areas of future research work to be followed are discussed and possible new industrial applications mentioned.     

The porosity dependence of sound velocities in ceramic materials

The porosity dependence of transverse and longitudinal sound wave velocities is studied in statistically isotropic porous ceramics. Based on the model relations for elastic moduli six model relations are constructed for the prediction of the porosity dependence of these velocities. All of them predict a decrease of sound wave velocities with increasing porosity, but the Maxwell / Mori-Tanaka / MMT model leads to unrealistic predictions for high porosity. A velocity ratio function is defined which contains the porosity dependence of the effective Poisson ratio and enables the prediction of longitudinal wave velocities. A comparison with literature data shows that most data lie below the exponential prediction and above the numerical prediction for concave pores. The correlation of the normalized longitudinal wave velocities and relative transverse wave velocities shows that essentially all values are above the highest lower bound and are reasonably predicted by the differential, exponential and self-consistent models.     

The Coupled FEM Analysis of the Transient Temperature Field During Inertia Friction Welding of GH4169 Alloy

The inertia friction welding process is a non-linear process because of the interaction between the temperature field and the material properties as well as the friction force. A thermo-mechanical coupled finite element model is established to simulate the temperature field of this process. The transient temperature distribution during the inertia friction welding process of two similar workpieces of GH4169 alloy is calculated. The region of the circular cross-section of the workpiece is divided into a number of four-nodded isoparametric elements. In this model, the temperature dependent thermal properties, time dependent heat inputs, contact condition of welding interface, and deformation of the flash were considered. At the same time, the convection and radiation heat losses at the surface of the workpieces were also considered. A temperature data acquisition system was developed. The temperature at some position near the welding interface was measured using this system. The calculated temperature agrees well with the experimental data. The deformation of the flash and the factor affecting the temperature distribution at the welding interface are also discussed.     

A New Strategy for Restraining Dynamic Strain Aging in GH4169 Alloy During Tensile Deformation at High Temperature

The dynamic strain aging(DSA) behavior was investigated in GH4169 alloy during tensile deforming with electric-pulse current(EPC) at 750 ℃.The results show that DSA is restrained in the alloy when deformed with 40 Hz-EPC.The size ofγ " phase inner grains increases obviously and δ phase is facilitated to precipitate on grain boundary in the alloy applied with EPC,due to the promotion effect of EPC on the diffusion and segregation of atoms.Transmission electron microscopy(TEM)results indicate that...     

Graphyne-based carbon allotropes with tunable properties: From Dirac fermion to semiconductor

Inserting acetylenic bonds into the framework of graphene leads to a novel carbon allotrope family named as graphyne and graphdiyne, one of the graphyne, has been synthesized. Here, we focus on the graphyne with all the covalent bonds of graphene being replaced by sp²–sp…sp–sp² linkages (α-graphyne) and its three-dimensional (3D) derivatives. We predicted that regardless of the length of the acetylenic linkages, α-graphyne has linear energy-momentum dispersion relations which cross at the Dirac point characterized by Dirac fermion, similar to graphene. The Fermi velocity is also comparable to graphene. The Dirac fermion characteristics are preserved in the multi-layered α-graphyne with AA stacking mode, where the AB stacking mode leads to a parabolic dispersion relation at the K point. We also proposed that α-graphyne may convert to more stable 3D porous structures whose energies are even comparable to diamond. More interestingly, some exceptional properties of these carbon foams, such as lower hardness, tunable electronic properties ranging from metal to semiconductor, and strong adsorption in the visible light region have been predicted from first-principles calculations. The realization of these novel graphyne-based carbon materials may not only enrich the databases of carbon allotrope family but also find applications in wide-range fields, such as electronic devices, shape-selective catalysts, molecular sieves, and solar cells.