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This work designed a facile preparation for an SiO2/C composite as the anode material for lithium ion battery. Both SiO2 and carbon are amorphous. SiO2 and carbon are mixed uniformly. The SiO2/C composite shows high specific capacity, cycle stability, and rate capability in lithium ion battery charge–discharge test. A stable reversible capacity of 1024 mA h/g at the current density of 100 mA/g is reached. The capacity retains 83% after 100 cycles. The uniform mixture of SiO2 and carbon leads to reduced volume change during the lithiation and delithiation of SiO2, together with the amorphous nature of SiO2 explains the high cycling stability. The carbon coating is a key factor for the high capacity and stability due to the increased electrical conductivity and reduced volume change. The resistance of the solid electrolyte interface film and charge transfer resistance of the SiO2/C composite are much smaller than those of pure carbon, which is a direct proof of the improved conductivity of the material by the carbon coating.
A TiO2/carbon nanotubes (TiO2/CNTs) composite was synthesized by chemical vapor deposition method with in situ growth of CNTs using hydrothermally treated TiO2 as the starting material. The nanocomposite was characterized by powder x-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, Raman spectrum, and nitrogen adsorption/desorption isotherms and was investigated as an anode material for lithium-ion batteries. The underlying mechanism for the improvement was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. The in situ synthesized composite showed better electrochemical performance than the pristine TiO2. The in situ formed CNTs not only supply an efficient conductive network but also keep the structural stability of the TiO2 particles, leading to improved electrochemical performance.
This study reviews the results of the surgical management of 154 cases of ruptured aneurysm of the sinus of Valsalva. Of the patients0 73% were male, with an average age of 28 years. An associated ventricular septal defect was found in 40% and 23% had aortic valvar regurgitation. The aneurysms originated from the right coronary sinus in 79% and from the non-coronary sinus in the remainders. The aneurysms ruptured into the right ventricle in 73%, into the right atrium in 27% and into the left ventricle in less than 1%. Operative mortality was 4.5%. Long-term follow-up was achieved in 80% of patients, with a mean duration of 5.7 years and a range from two months to 29 years. Preoperative aortic regurgitation and preoperative functional class (NYHA III or IV) were both predictive of a worse long-term outcome. The optimal surgical approach was closure of the distal end of the fistula by direct suture together with reinforcement of the aortic sinus with a Dacron patch.
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