Diffusion behavior and distribution regulation of MgO in MgO-bearing pellets

In this paper, the diffusion behavior between MgO and Fe2O3（the main iron oxide in pellets） is investigated using a diffusion couple method. In addition, the distribution regulation of MgO in MgO-bearing pellets is analyzed via pelletizing experiments. The results illustrate that MgO is prone to diffuse into Fe2O3 in the form of solid solution; the diffusion rate considered here is 13.64 μm·min^（-1）. Most MgO content distributes in the iron phase instead of the slag phase. The MF phase {（Mg（1-x）Fex）O·Fe2O3, x ≤ 1} is generated in the MgO-bearing pellets. However, the distribution of MgO in the radial direction of the pellets is inconsistent. The solid solution portion of MgO in the MF phase is larger in the outer layer of the pellets than in the inner layer. In this work, the approximate chemical composition of the MF phase in the outer layer of the pellets is {（Mg（0.35-0.77）·Fe（0.65-0.23）） O·Fe2O3} and in the inner layer is {（Mg（0.13-0.45）·Fe（0.87-0.55））O·Fe2O3}.

Effect of MgO on Oxidation Process of Fe_3O_4 in Pellets

Induration process of oxidized pellets involves the oxidation of Fe3O4 and re-crystallization of Fe2O3.The oxidation process of Fe3O4 is significant for pellets to obtain better ambient strength.Thus,the effect of MgO on oxidation process of Fe3O4 was investigated.The unreacted core model was applied to analyze the oxidizing induration process of pellets.The experimental results show that MgO plays a negative role in the oxidation process of Fe3O4.The oxidation rate of Fe3O4 in MgO-fluxed pellets（95.0% Fe3O4 ＋5.0% MgO）is slower than that in standard acid pellets（100% Fe3O4）.The relation between oxidation ratio of Fe3O4 and time was calculated based on the unreacted core model for both MgO-fluxed pellets and standard acid pellets.According to verification experiments,the values calculated by model coincide well with the experimental values.Therefore,the unreacted core model could be applied to describe the oxidizing induration process of pellets.

Effects of Surgical Ventricular Restoration on Left Ventricular Shape, Size, and Function for Left Ventricular Anterior Aneurysm

Background： Surgical ventricular restoration （SVR） has been performed to treat left ventricular （LV） aneurysm. However, there is limited analysis of changes in LV shape. This study aimed to evaluate the changes in LV shape induced by SVR and the effects of SVR on LV size and function for LV aneurysm. Methods： Between April 2006 and March 2015, 18 patients with dyskinetic （dyskinetic group） and 12 patients with akinetic （akinetic group） postinfarction LV anterior aneurysm receiving SVR with the Dor procedure at Chinese People＇s Liberation Army General Hospital were enrolled in this study. A retrospective analysis was carried out using data from the echocardiography database. LV shape was analyzed by calculating the apical conicity index （ACI）. LV end-diastolic volume index, end-systolic volume index, and ejection fraction （EF） were measured. One-way analysis of variance was used to compare means at different time points within each group. Results： Within one week after SVR, LV shape became more conical in the two groups （ACI decreased from 0.84 ± 0.13 to 0.69 ± 0.11 [t = 5.155, P = 0.000] in dyskinetic group and from 0.73 ± 0.07 to 0.60 ± 0.11 [t = 2.701, P = 0.026] in akinetic group; LV volumes were decreased significantly and became closer to normal values and EF was improved significantly in the two groups）. On follow-up at least one year, LV shape remained unchanged in dyskinetic group （ACI increased from 0.69 ± 0.11 to 0.74 ± 0.12, t = - 1.109, P = 0.294）, but became more spherical in akinetic group （ACI significantly increased from 0.60 ± 0.11 to 0.75 ±0.11, t = -I .880, P = 0.047）; LV volumes remained unchanged in dyskinetic group, but increased significantly in akinetic group and EF remained unchanged in the two groups. Conclusions： SVR could reshape LV to a more conical shape and a more normal size and improve LV function significantly early after the procedure in patients with dyskinetic or akinetic postinfarction LV anterior aneurysm. However, LV tends to be more spherical and enlarged in the akinetic group on at least 1-year follow-up.