Harbin Engineering University

About: Harbin Engineering University is a education organization based out in Harbin, Heilongjiang, China. It is known for research contribution in the topics: Control theory & Computer science. The organization has 31149 authors who have published 27940 publications receiving 276787 citations. The organization is also known as: HEU.

HyFlex nickel-titanium rotary instruments after clinical use: metallurgical properties.

Abstract: Shen Y, Coil JM, Zhou H, Zheng Y, Haapasalo M. HyFlex nickel–titanium rotary instruments after clinical use: metallurgical properties. International Endodontic Journal, 46, 720–729, 2013. Aim To analyse the type and location of defects in HyFlex CM instruments after clinical use in a graduate endodontic programme and to examine the impact of clinical use on their metallurgical properties. Methodology A total of 468 HyFlex CM instruments discarded from a graduate endodontic programme were collected after use in three teeth. The incidence and type of instrument defects were analysed. The lateral surfaces of the defect instruments were examined by scanning electron microscopy. New and clinically used instruments were examined by differential scanning calorimetry (DSC) and x-ray diffraction (XRD). Vickers hardness was measured with a 200-g load near the flutes for new and clinically used axially sectioned instruments. Data were analysed using one-way ANOVA or Tukey’s multiple comparison test. Results Of the 468 HyFlex instruments collected, no fractures were observed and 16 (3.4%) revealed deformation. Of all the unwound instruments, size 20, .04 taper unwound the most often (n = 5) followed by size 25, .08 taper (n = 4). The trend of DSC plots of new instruments and clinically used (with and without defects) instruments groups were very similar. The DSC analyses showed that HyFlex instruments had an austenite transformation completion or austenite-finish (Af) temperature exceeding 37 °C. The Af temperatures of HyFlex instruments (with or without defects) after multiple clinical use were much lower than in new instruments (P < 0.05). The enthalpy values for the transformation from martensitic to austenitic on deformed instruments were smaller than in the new instruments at the tip region (P < 0.05). XRD results showed that NiTi instruments had austenite and martensite structure on both new and used HyFlex instruments at room temperature. No significant difference in microhardness was detected amongst new and used instruments (with and without defects). Conclusions The risk of HyFlex instruments fracture in the canal is very low when instruments are discarded after three cases of clinical use. New HyFlex instruments were a mixture of martensite and austenite structure at body temperature. Multiple clinical use caused significant changes in the microstructural properties of HyFlex instruments. Smaller instruments should be considered as single-use.

Facile preparation of three-dimensional Ni(OH)2/Ni foam anode with low cost and its application in a direct urea fuel cell

Abstract: Three-dimensional Ni(OH)2/Ni foam electrodes with low cost are simply fabricated via a template-free growth method and employed as efficient anodes for a direct urea–hydrogen peroxide fuel cell (DUPFC). The surface morphologies of Ni(OH)2 catalysts on the electrodes can be easily controlled by altering the reaction temperatures. The nano-sheet (NS) Ni(OH)2/Ni foam electrode exhibits highest catalytic activity towards urea electro-oxidation among the four electrodes. The oxidation current density of the NS Ni(OH)2/Ni foam electrode reaches 337 mA cm−2 at 0.45 V (vs. Ag/AgCl) with a low onset oxidation potential in 0.6 mol L−1 urea and 5 mol L−1 KOH solutions. The DUPFC using NS Ni(OH)2/Ni foam anode shows an open circuit voltage of 0.86 V and high peak power density of 19.7 mW cm−2 and 28.8 mW cm−2 at 20 °C and 50 °C, respectively, which is much higher than the performance of direct urea fuel cells reported previously. The outstanding cell performance using a cheap NS Ni(OH)2/Ni foam anode indicates DUPFC is a promising new type of fuel cell.

Understanding the effect of depressing surface moisture sensitivity on promoting sodium intercalation in coral-like Na3.12Fe2.44(P2O7)2/C synthesized via a flash-combustion strategy

Abstract: The low-cost sodium iron pyrophosphate Na3.12Fe2.44(P2O7)2, which enables facile ion transport, presents a promising alternative for use as the cathode of sodium ion batteries. However, high moisture sensitivity and severe surface oxidation lead to a large irreversible capacity and inferior electrochemical kinetics. Herein, for the first time, we report the design of an ultrafast “flash-combustion synthesis” strategy to prepare coral-like Na3.12Fe2.44(P2O7)2/C with good surface properties and fast sodium intercalation. The single-phase Na3.12Fe2.44(P2O7)2 is successfully prepared in as short a time as three minutes. Each ultrafine Na3.12Fe2.44(P2O7)2 particle with a nanoscale carbon coating is enwrapped in a microscale carbon matrix, forming a coral-like architecture. Benefiting from the hierarchical carbon decoration, the coral-like composite attains good surface properties that enable low moisture sensitivity and fast sodium intercalation. Moreover, dynamic analysis reveals that surface oxidation proceeds through a “shell–core” mechanism and demonstrates the crucial role of the surface properties on sodium intercalation. Taking advantage of the good surface properties and the hierarchical porous architecture, the coral-like composite is capable of fast sodium intercalation and stable prolonged cycling. It retains 95% of the initial capacity after 200 cycles alternating between 20 and 5C rates. The clarification of the correlation between the surface properties and the sodium intercalation chemistry provides clues to the design and construction of high-performance Na3.12Fe2.44(P2O7)2 for large-scale applications.