ABSTRACT
To provide the basis for thermal conductivity regulation of vermicular graphite cast iron (VGI), a new theoretical method consisting of shape interpolation, unit cell model and numerical calculation was proposed. Considering the influence of the graphite anisotropy and interfacial contact thermal conductivity (ICTC), the effective thermal conductivity of a series of unit cell models was calculated by numerical calculation based on finite difference. The effects of microstructure on effective thermal conductivity of VGI were studied by shape interpolation. The experimental results were in good agreement with the calculated ones. The effective thermal conductivity of VGI increases in power function with the decrease in graphite shape parameter, and increases linearly with the increase in graphite volume fraction and thermal conductivity of matrix. When the graphite volume fraction increases by 1%, the thermal conductivity of nodular cast iron increases by about 0.18 W/(m·K), while that of gray cast iron increases by about 3 W/(m·K). The thermal conductivity of cast iron has the same sensitivity to the thermal conductivity of matrix regardless of the graphite shape parameter. The thermal conductivity of matrix increased by 15 W/(m·K) and the thermal conductivity of cast iron increased by about 12 W/(m·K). Moreover, the more the graphite shape deviates from the sphere, the greater the enhancement effect of graphite anisotropy on thermal conductivity than the hindrance effect of interface between graphite and matrix. This work can provide guidance for the development of high thermal conductivity VGI and the study of thermal conductivity of composites containing anisotropic dispersed phase particles with complex shapes.
ABSTRACT
OBJECTIVE: To compare the analytical method of LC-UV and LC-MS determination of major polyphenolic components in leaves of Crataegus L. METHODS: By high-performance liquid chromatography method with VWD and MSD, Lichropsher C18 column (250 x 4.6 mm I.D., 5 microm); mobile phase consisted of solvent A (acetonitrile) and solvent B (0.05% formic acid) ; elution profile was: 0-12 min 11% to 17% A in B (linear gradient), 12-30 min 17% to 18% A in B (linear gradient), 30-45 min 18% to 40% A in B (linear gradient), 45-60 min 40% to 100% A in B (linear gradient); flow rate was 1.00 ml/min, flow into MSD and VWD by diffluence, column temperature 30 degrees C and the injection volume 10 microl. RESULT: The sensitivity of LC-MS was 10 times more than that of LC-UV, so it is preponderance for microanalysis. Additionally, because LC-MS can identify the component by retention time (t(R)) and m/z, it has high selectivity and exclusion for the determined component. However, the method of LC-UV is simple; the cost is lower; the separate effect is better. So it is preponderance to determine the higher content component, which has better separate effect. CONCLUSION: LC-UV and LC-MS exhibited their own predominance for determination of major polyphenolic components in leaves of Crataegus L. So the detector should be selected according to the determined targets.
