The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy,scanning electron microscopy and tensile test.ZK60 alloys were prepared...The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy,scanning electron microscopy and tensile test.ZK60 alloys were prepared by changing holding time of alloy melt during semi-continuous casting in order to control the content of impurity elements.The alloy with lower purity content is found to have less second precipitates and larger grain size in the as-cast state.However,in the as-extruded state,reducing impurities brings about a decrease in grain size and an increase in yield strength from 244 MPa to 268 MPa,while the elongations in the as-extruded alloys with different contents of impurities are almost the same.After T5 treatment,impurity content is found to have more obvious effect on the yield strength of ZK60 alloy.The yield strength of ZK60-45 alloys with low impurity content is increased up to 295 MPa after T5 treatment.展开更多
The galvanic corrosion behavior of metal-matrix composite plain carbon steel/boron carbide （B4C） in 3.5% NaCl solution was studied. The composite was locally produced as a weld band on carbon steel by means of the g...The galvanic corrosion behavior of metal-matrix composite plain carbon steel/boron carbide （B4C） in 3.5% NaCl solution was studied. The composite was locally produced as a weld band on carbon steel by means of the gas tungsten arc welding process and using nickel as the wetting agent. Samples from the weld band, heat-affected zone and parent metal region were extracted precisely and DC/AC electrochemical tests in combination with techniques such as scanning electron microcopy and energy dispersive spectrometry were conducted. The results of the electrochemical tests show that the corrosion resistance of the parent metal sample is higher than that of the welded composite and the HAZ samples. However, as the corrosion potential （Eco^r） of the parent metal is more positive than other two samples, this becomes the cathode in galvanic couples with two other samples. On the other hand, the weld composite sample is also cathodic due to its more positive Ecorr compared to HAZ sample. This means that the HAZ can be particularly at risk of preferential dissolution. The approach can be used in specific areas on plain carbon steel to locally increase hardness and resistance to abrasion and reduce manufacturing costs.展开更多
Background In order to acquire a high quality image with a low radiation dose, prospective electrocardiogram （ECG）-triggered computed tomography coronary angiography （CTCA） requires a stable heart rate （HR） 〈 6...Background In order to acquire a high quality image with a low radiation dose, prospective electrocardiogram （ECG）-triggered computed tomography coronary angiography （CTCA） requires a stable heart rate （HR） 〈 65 beats/min. Esmolol has the advantage of reduc-ing HR. The objective of this article is to assess the value of intravenous esmolol treatment before prospective ECG-tr/ggered high-pitch spiral acquisition for CTCA. Methods From March 2013 to June 2013, 313 patients underwent prospective ECG-triggered CTCA. Two hundred and thirty two of them received esmolol before angiography. We retrospectively analyzed clinical characteristics, esmolol dose, radiation exposure dose, and the change in HR and blood pressure in these 232 patients. Results A total of 232 patients with a HR 〉 65 beats/rain before CTCA examination received intravenous esmolol treatment （mean dose of 57.26±15.39 rag）, The mean initial HR （HR1）, slowest HR （HR2）, and the HR 30 min after HR2 （HR3） were 75.06± 5.59, 60.75 ±4.00, and 75.54 ± 5.96 beats/min, respectively （HR1 vs. HR2, P 〈 0.0001; HRI vs. HR3, P = 0.377）. The mean time from esmolol administration to HR2 was 24.25 ± 4.97 s and the mean effective radiation dose was 2.28 ± 0.02 mSv. Conclusions HR could be rapidly controlled at an optimum level with intravenous esmolol before prospective ECG-triggered high-pitch spiral acquisition for CTCA. Consequently, the patients received a very low radiation dose.展开更多
ZrTiO4 is a small ceramic constituent material which has very good thermal and electrical properties. ZrTiO4 thin films were deposited by reactive dc magnetron co-sputtering method. The crystal structure, surface morp...ZrTiO4 is a small ceramic constituent material which has very good thermal and electrical properties. ZrTiO4 thin films were deposited by reactive dc magnetron co-sputtering method. The crystal structure, surface morphology, thickness and dielectric properties were characterized by XRD （X-ray diffraction）, AFM （atomic force microscopy）, FE-SEM （field emission scanning electron microscope）, and precision impedance analyzer respectively. These films were crystallization of the orthorhombic phase （111） of ZrTiOa. The microstructure of well-crystallized ZrTiO4 thin films had the surface morphology was smooth with 1.695 nmrms roughness. The high dielectric constant width decreases from 129.2 to 110.6 when sputtering current increases which are higher more than that had researched because of higher energy but impedance; ｜Z｜ increases from 1.97 to 2.47 kΩ. These results are consistent with the RMS roughness results, which are the RMS roughness decrease with increasing sputtering current.展开更多
基金Project(50725413)supported by the National Natural Science Foundation of ChinaProject(2007CB613704)supported by the National Basic Research Program of ChinaProject(20090191120013)supported by the PhD Program Foundation of Ministry of Education of China
文摘The influence of impurity content on the microstructure and mechanical properties of ZK60 magnesium alloys was investigated by optical microscopy,scanning electron microscopy and tensile test.ZK60 alloys were prepared by changing holding time of alloy melt during semi-continuous casting in order to control the content of impurity elements.The alloy with lower purity content is found to have less second precipitates and larger grain size in the as-cast state.However,in the as-extruded state,reducing impurities brings about a decrease in grain size and an increase in yield strength from 244 MPa to 268 MPa,while the elongations in the as-extruded alloys with different contents of impurities are almost the same.After T5 treatment,impurity content is found to have more obvious effect on the yield strength of ZK60 alloy.The yield strength of ZK60-45 alloys with low impurity content is increased up to 295 MPa after T5 treatment.
文摘The galvanic corrosion behavior of metal-matrix composite plain carbon steel/boron carbide （B4C） in 3.5% NaCl solution was studied. The composite was locally produced as a weld band on carbon steel by means of the gas tungsten arc welding process and using nickel as the wetting agent. Samples from the weld band, heat-affected zone and parent metal region were extracted precisely and DC/AC electrochemical tests in combination with techniques such as scanning electron microcopy and energy dispersive spectrometry were conducted. The results of the electrochemical tests show that the corrosion resistance of the parent metal sample is higher than that of the welded composite and the HAZ samples. However, as the corrosion potential （Eco^r） of the parent metal is more positive than other two samples, this becomes the cathode in galvanic couples with two other samples. On the other hand, the weld composite sample is also cathodic due to its more positive Ecorr compared to HAZ sample. This means that the HAZ can be particularly at risk of preferential dissolution. The approach can be used in specific areas on plain carbon steel to locally increase hardness and resistance to abrasion and reduce manufacturing costs.
文摘Background In order to acquire a high quality image with a low radiation dose, prospective electrocardiogram （ECG）-triggered computed tomography coronary angiography （CTCA） requires a stable heart rate （HR） 〈 65 beats/min. Esmolol has the advantage of reduc-ing HR. The objective of this article is to assess the value of intravenous esmolol treatment before prospective ECG-tr/ggered high-pitch spiral acquisition for CTCA. Methods From March 2013 to June 2013, 313 patients underwent prospective ECG-triggered CTCA. Two hundred and thirty two of them received esmolol before angiography. We retrospectively analyzed clinical characteristics, esmolol dose, radiation exposure dose, and the change in HR and blood pressure in these 232 patients. Results A total of 232 patients with a HR 〉 65 beats/rain before CTCA examination received intravenous esmolol treatment （mean dose of 57.26±15.39 rag）, The mean initial HR （HR1）, slowest HR （HR2）, and the HR 30 min after HR2 （HR3） were 75.06± 5.59, 60.75 ±4.00, and 75.54 ± 5.96 beats/min, respectively （HR1 vs. HR2, P 〈 0.0001; HRI vs. HR3, P = 0.377）. The mean time from esmolol administration to HR2 was 24.25 ± 4.97 s and the mean effective radiation dose was 2.28 ± 0.02 mSv. Conclusions HR could be rapidly controlled at an optimum level with intravenous esmolol before prospective ECG-triggered high-pitch spiral acquisition for CTCA. Consequently, the patients received a very low radiation dose.
文摘ZrTiO4 is a small ceramic constituent material which has very good thermal and electrical properties. ZrTiO4 thin films were deposited by reactive dc magnetron co-sputtering method. The crystal structure, surface morphology, thickness and dielectric properties were characterized by XRD （X-ray diffraction）, AFM （atomic force microscopy）, FE-SEM （field emission scanning electron microscope）, and precision impedance analyzer respectively. These films were crystallization of the orthorhombic phase （111） of ZrTiOa. The microstructure of well-crystallized ZrTiO4 thin films had the surface morphology was smooth with 1.695 nmrms roughness. The high dielectric constant width decreases from 129.2 to 110.6 when sputtering current increases which are higher more than that had researched because of higher energy but impedance; ｜Z｜ increases from 1.97 to 2.47 kΩ. These results are consistent with the RMS roughness results, which are the RMS roughness decrease with increasing sputtering current.
