Effect of Sodium Borate on the Preparation of TiN from Titanomagnetite Concentrates by Carbothermic Reduction–Magnetic Separation and Acid Leaching Process

Carbothermic reduction–magnetic separation and acid leaching processes were used to produce TiN and direct reduced iron (DRI) from titanomagnetite concentrates. The effects of sodium borate on the reduction behavior of TMCs, the magnetic separation of the reduced products, and the purification of the impure TiN by acid leaching were investigated. Results of x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis showed that magnesium aluminate spinel (MgAl2O4) was generated in the reduced products, which could hinder the purification of the TiN. Adding sodium borate not only inhibited the formation of MgAl2O4, but also promoted the formation of TiN by decreasing the roasting temperature and time. Adding sodium borate slightly affected the separation of metallic Fe and TiN. By adding 16% sodium borate, a DRI with 94.3% Fe, 0.6% Ti, and 0.1% V was obtained by magnetic separation. After HCl + HF leaching, the TiN product containing 74.1% Ti and 2.8% V was obtained with the Ti recovery of 94.6% and V recovery of 58.3%

Preparation of Direct Reduced Iron and Titanium Nitride from Panzhihua Titanomagnetite Concentrate Through Carbothermic Reduction-Magnetic Separation

A novel process for preparing direct reduction iron (DRI) and titanium nitride (TiN) from Panzhihua titanomagnetite concentrate is proposed. This process involves pelletizing, direct reduction roasting and magnetic separation. The effects of reduction temperature, coal dosage and reduction time on the phase transformation of composite pellets were investigated by X-ray diffraction. Results show that TiN formation proceeds less easily than metallic iron formation. Increasing the reduction temperature, reduction time and coal dosage can promote the transformation of titanium to TiN. Titanium was almost completely transformed into TiN under the conditions of 1300 °C reduction temperature, 26 wt % coal dosage and 90 min reduction time. The scanning electron microscopy (SEM) analysis showed that near-spherical metallic iron particles with diameters from dozens of microns to about 300 μm were formed in the reduced pellets, whereas the TiN particles generally measured less than 10 μm. The energy dispersive spectroscopy (EDS) results revealed that the TiN phase contains a certain amount of vanadium and carbon, and traces of other impurities. The reduced composite pellets under the optimum conditions were processed by grinding and subsequent magnetic separation. As a result, a DRI with 92.88 wt % Fe, 1.00 wt % Ti, and 0.13 wt % V was obtained, and the recoveries of Fe, Ti, and V were 92.85 wt %, 9.00 wt %, and 19.40 wt %, respectively. 91.00 wt % Ti and 80.60 wt % V were concentrated in the rough TiN concentrate

Allosteric-activation mechanism of BK channel gating ring triggered by calcium ions.

Calcium ions bind at the gating ring which triggers the gating of BK channels. However, the allosteric mechanism by which Ca2+ regulates the gating of BK channels remains obscure. Here, we applied Molecular Dynamics (MD) and Targeted MD to the integrated gating ring of BK channels, and achieved the transition from the closed state to a half-open state. Our date show that the distances of the diagonal subunits increase from 41.0 Å at closed state to 45.7Å or 46.4 Å at a half-open state. It is the rotatory motion and flower-opening like motion of the gating rings which are thought to pull the bundle crossing gate to open ultimately. Compared with the 'Ca2+ bowl' at RCK2, the RCK1 Ca2+ sites make more contribution to opening the channel. The allosteric motions of the gating ring are regulated by three group of interactions. The first weakened group is thought to stabilize the close state; the second strengthened group is thought to stabilize the open state; the third group thought to lead AC region forming the CTD pore to coordinated motion, which exquisitely regulates the conformational changes during the opening of BK channels by Ca2+

The dynamic motion during gating ring opening from the TMD simulation on RCK1 sites.

<p>(A) and (B) show the first principal component of the two motion tendency of gating ring during the TMD simulation on the RCK1 sites.</p

The gating ring achieved a half-open state after targeted MD simulation.

<p>(A) The schematic diagram of closed state, the target force is applied to those residues (His365-Asp369, Ser512-Phe516, and Ser533-Tyr537) and (Asn887-Pro899), which are colored in green and yellow, respectively. The main conformational difference happens in the AC region (blue). (B) The evolution of RMSDs from the initial RMSD at the first TMD step to the final RMSD at the last TMD step. (C) RMSDs are calculated based on all the Cα atoms of gating ring along the TMD simulations compared to the target structure.</p

Time course of interactions that regulate the gating of BK channels.

<p>(A), (B), and (C) show the time course of the interactions between D362 and S925, D367 and S515, S515 and Y904. (D), (E) and (F) show the time course of the interactions between R342 and E374, D369 and R648, R653 and D931. (G, H) The time course of the interactions between L360 and H394, N358 and D921.</p

Schematic diagrams of the structures and RMSDs of BK gating ring.

<p>(A, B) Schematic diagrams of the structures of BK gating ring in closed and open states, respectively. Cα atoms of Lys343 and Asn384, and Ca²⁺ are represented as black ball, red ball, and magenta ball, respectively. RCK1 site and Ca²⁺ bowl are highlighted as green and yellow, respectively. (C, D) The RMSDs were calculated based on all the Cα atoms of the BK gating ring for close and open states, respectively.</p