Vol 7 No 1 (2025)

• Spent Potlining from Aluminium Electrolysis-Are Cells with Vertical Inert Electrodes a Solution?

  Jón Hjaltalín Magnússon, Halvor Kvande

  Spent potlining (SPL) is a term used in the aluminium industry for the spent cathode lining materials of industrial electrolysis cells. SPL is the cathode and sidewall materials that are removed from a cell after being shut down. The treatment of spent potlining is an environmental problem that has been a challenge for a long time and it needs to be solved. Sodium ions are the main carrier of electrical current through the molten cryolite bath during electrolysis, and a small amount of sodium metal is formed as part of the cathode reaction. Sodium penetrates the porous horizontal carbon cathode blocks in the bottom of the cell and causes swelling of the carbon material. With the present cell design it is not possible to eliminate this sodium interaction, and the only way to avoid it is to use a different cell design. The present paper discusses whether the use of cells with vertical inert electrodes will give less sodium penetration in the carbon part of the cell.

  PDF

• Cauchy Pressure and Valence Electron Concentration Dominated Hardness of Multi-principal Element Carbides Ceramics

  Zhigang Ding

  Recent studies indicate that multi-principal element carbides (MPECs) ceramics can simultaneously possess high hardness and high toughness, which have potential applications in industrial fields. Nevertheless, microstructural origins of the excellent hardness and toughness combination remain unclear. In present study, the hardness of 38 derivatives based on (Ti-Zr-Hf-V-Nb-Ta)C MPECs were researched by density functional theory calculations. We found that that the non-linear equation combination by Cauchy pressure P_c and valence electron concentration (VEC) show high prediction accuracy (R² = 0.91) with DFT values. The multivariate regression surface of hardness reveals that high hardness is often associated with high VEC and low Cauchy pressure, which can be used to predict the hardness of MPECs.

  PDF

• Influence of the Addition of Niobium Pentoxide on the Structural Properties of Hydroxyapatite

  José Adauto da Cruz, Rogério Ribeiro Pezarini, Stephen Rathinaraj Benjamin, Rogério Ribeiro Pezarini, Paulo Maria de Oliveira Silva, Antonio Jefferson Mangueira Sales, Fernandes GraçaManuel Pedro

  The study focused on investigating the properties of composites made from natural hydroxyapatite (HAp, Ca₁₀(PO₄)₆(OH)₂) sourced from tilapia fish bones (Oreochromis niloticus) and niobium pentoxide (PNb, Nb₂O₅). The effects of PNb concentration and sintering temperature were examined. Composites were created using a constant pressure of 450 MPa following the formula (100-x)HAp + (x)PNb, with x varying in increments of 10%, and then sintered at temperatures ranging from 700 to 1300 °C. X-ray diffraction (XRD) analysis showed the formation of new phases based on the PNb concentration and temperature. Rietveld refinement confirmed a strong fit with experimental data, supporting the accuracy of the model parameters. Fourier Transform Infrared Spectroscopy with Photoacoustic Detection (FTIR-PAS) revealed the disappearance of the OH^- functional group at 3572 cm^-¹. Raman spectroscopy results were consistent with XRD findings. Scanning Electron Microscopy (SEM) showed complex microstructures influenced by composition, sintering temperature, and phase interactions, with liquid-phase sintering contributing to microstructural changes. Energy Dispersive X-ray Spectroscopy (EDS) provided semiquantitative analysis, detecting the primary elements Ca, P, and Nb, along with smaller amounts of Mg and Na. The Vickers Hardness (VH) measurements indicated that PNb concentration significantly affects the mechanical properties of the composite. The study suggests that HAp/PNb composites, influenced by temperature and PNb concentration, hold great potential for use in orthopedic and dental biomaterials.

  PDF