| Porous metal fiber sintered sheet(PMFSS)as a novel structural and functional engineering material has been widely carried out in many fields such as catalytic reaction,filtration and separation,heat transfer,noise control,electromagnetic shielding and so on.Because it possess the structural properties like tri-dimensional pore structure,large specific surface,high porosity and exhibits good thermal and electrical conductivity,excellent wear and corrosion resistance,high strength and flexibility.In this dissertation,the metal fibers are fabricated by a multi-tooth tool to obtain rough surface morphology,and formed into different porous metal fiber sintered sheet using the low-temperature solid-phase sintering technology.The properties of porous copper fiber sintered sheet(PCFSS)like tensile strength,pressure drop,thermal conductivity,and sound absorption were experimental investigated respectively.Main research results are as follows:1.Fabrication of continuous slim metal fibers using a multi-tooth toolA novel multi-tooth tool was designed to fabricate continuous,slim metal fibers on a common horizontal lathe.Following an analysis of the process of the fabrication of metal fibers,we designed a geometric cutting model of the multi-tooth tool with a large inclination to form continuous,slim metal fibers.The effect of cutting parameters on the equivalent diameter and the surface morphology of the metal fibers was experimental investigated.Finally,the copper fibers and aluminum fibers with rough surface and equipment diameter under 100?m was manufactured.2.Manufacturing of PMFSS and its mechanical property testingBy designing different molds,copper fibers were used as raw materials to form into porous copper fibers sintered sheets by a low-temperature solid-phase sintering technology at 950? for 30 min.During the process of mold pressing and sintering,the formation of sintering joints and mechanical intersection improves the tensile strength.The tin-lead welding method can meet the demand of welding different PCFSSs.And the tensile strength value of welded sheets is roughly 70%-75%of its raw materials.Also,the manufacturing of PMFSS with continuous gradient pore structure can be achieved by designing a molded device with variable volume.3.Press drop characteristic measurements of PCFSSThe effect of porosity,thickness on the press drop characteristics was investigated when deionized water flow through the PCFSS.The press drop decreases with the porosity increasing and thickness decreasing.Through numerical analysis,the flow resistance of porous copper fiber sintered sheet is mainly affected by porosity,also the flow resistance is associated with the geometrical shapes of testing sample.4.Thermal conductivity measurements of PCFSSA novel reference plate method(RPM)with a steady state heat transfer process is introduced to measure the thermal conductivity of PCFSS.Compared with red copper plate,when the 304 stainless steel is selected as the reference plate,the measurement results are relatively reliable.At the porosity of 70%-90%,the thermal conductivity increases with decreases in the porosities of PCFSSs.The thermal conductivities of PCFSSs with porosities of 70%,80%and 90%at the measuring temperature region in the approximate temperature range of 35-65? correspond to 25.35,5.01 and 11.24 W/(m·?),respectively.The thermal conductivity of 70%-80%-90%gradient porosity PCFSS is between the thermal conductivities of 80%and 90%porosity PCFSSs.5.Sound absorption properties of PCFSSThe sound absorption coefficients of PCFSSs are measured by the impedance tube method.Different parameters that affect the absorption coefficient are examined.The overall acoustic performance of PCFSSs with rough surface copper fibers is better than that with smooth ones.By increasing the PCFSS thickness,decreasing the porosity,and proper arrangement of porosity gradients,the sound absorption coefficients at low frequencies increase and the effective sound absorption frequency band widens,the overall acoustic performance improves. |
PDF Full Text Request