Papers by Keyword: Pore Characteristic

Abstract: The pore structure characteristics of reactive powder concrete (RPC) were investigated by means of the mercury injection method at seven temperature levels, namely, 20°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, respectively. The characteristic parameters such as porosity, pore volume, average pore size and threshold aperture varied with temperatures were analyzed. The results indicate that the porosity, pore volume, threshold aperture and other characteristic parameters of RPC increased with the temperature increasing.

Abstract: Gradient porous Ti was prepared by powder metallurgy method using NH4HCO3 as pore former. The effect of content and distribution of NH4HCO3 and sintering temperature on pore characteristic, sintering shrinkage, flexural property was studied. Stress-strain curves of gradient and uniform porous Ti material were compared. The results show the porosity, sintering shrinkage rate and flexural strength vary from 51.8% to 41.3%, from 23.5% to 28.7%, and from 145.7 MPa to 221.6 MPa when the distribution of NH4HCO3 varying form uniformity to gradient. Additionally, with the increase of sintering temperature, the porosity of gradient samples first increases and then decreases. When sintered at 1573K for 2h, the porosity of gradient porous Ti has the maximum of 45.6%. Moreover, there is pseudo yield phenomenon according to the test curve of three points bending of the gradient porous Ti with three layers structure.

Abstract: nkjet paper coating is a porous coating getting from a mixture of pigments, adhesives and a small amount of additives by way of coating and drying. Coating structure is defined as the coating thickness, porosity, pore size and its distribution, the surface and internal distribution of coating components. In which, pore characteristic (such as porosity, pore shape, pore size and its distribution) play an important role in the decision of absorption and spreading of ink droplet on inkjet paper. The commonly used detection methods of coating microstructure include image analysis and various physical detection methods. This paper selected 4 inkjet papers, and the two image analysis methods (SEM and AFM) were used to measure the pore characteristic of the testing coating, and characteristics of the two methods were analyzed and compared. And AFM observation method is more suitable for testing pore characteristics of inkjet paper coating, as it could provide more information on the microscopic morphology and coating composition. In the study of the structure of the coating surface, SEM and AFM have their own strengths and complement each other.

Abstract: High-property carbon refractories for blast furnaces should have high thermal conductivity and excellent porosity characteristics. The relationship between porosity characteristics and thermal conductivity of different graphite size (100mesh, 200mesh, 325mesh, 600mesh and 100mesh respectively) containing carbon refractories was investigated by using mercury porosimeter and laser thermal conductivity instrument. The results indicate that the thermal conductivity was reduced with the increase of porosity and <0.1μm pore volume as well as the decrease of mean pore diameter under the same condition, which was related to the short of thermal conductive route.

Abstract: Gradient porous NiTi alloys were fabricated by powder metallurgy method using NH₄HCO₃ as space-holder. The effect of content and distribution of NH₄HCO₃ on pore characteristic, phase composition and compressive properties was studied. The results showed the content of TiNi phase increased with the decrease of the content of NH₄HCO₃. When the distribution of NH₄HCO₃ varying form 12wt%-12wt%-12wt% to 12wt%-6wt%-12wt% and 12wt%-0wt%-12wt%, the stress and elastic modulus of porous NiTi alloys increased from 228MPa to 321MP and 446MPa, from 4.8GPa to 5.6GPa and 6.8GPa, respectively. Compared with uniform porous materials, gradient porous NiTi alloy exhibited better superelasticity.

Abstract: The method of the second intrusion mercury in MIP was used to investigate the pore characteristics of hardened cement paste with w/c ratio 0.23, 0.35 and 0.53, respectively, in order to research the quantitative relationship between transport properties and pore characteristics in cement-based composite materials. The results show the second intrusion mercury could well determine the effective pore structure parameters, and effective porosity accounts for 25% to 50% of total porosity in cement paste. At the same time, the existence of the first and second peak in pore size distribution curves is confirmed by MIP, such as, the first peak in hardened cement paste with water to cement ratio 0.53 is very distinct, however, with the decrease of water to cement ratio, the first peak gradually disappears. The pore diameter corresponding to the first and second peak is critical pore diameter of capillary pore and gel pore, respectively.

Abstract: Porous NiTi shape memory alloys were fabricated by thermal explosion method using different Ti and Ni powder as initial materials. The effect of process parameters including heating rate, and particle size of Ti on pore characteristic and phase composition was analyzed. Microstructure, phase composition, and mechanical properties were studied by SEM, XRD, and compression test, respectively. The mechanism of thermal explosion reaction was studied. The results show higher heating rate and smaller Ti particle size result in higher porosity and bigger pores. The thermal explosion reaction starts with the melting of a eutectic between β-Ti(Ni) and Ti2Ni and the main phases of as-reacted products are TiNi phase which are the desired phases. NiTi2 and TiNi3 phases are also present in small amounts. The content of TiNi phase increases with increasing heating rate or decreasing Ti particle size. The compressive strength and Young’s modulus of compacts decrease with the increase of the porosity.