Research On Preparation Technology Of Black Porous Alumina Ceramics

In view of the shortcomings of local elastic deformation of components in the traditional machining vacuum sucker when clamping the chip/film electronic components,Al₂O₃ as the base material,Ti O₂,Si O₂ as sintering additives,Fe₂O₃,CoO,Ni O and Mn O₂as black pigments,the black alumina ceramic formula was firstly explored by mould pressing.On this basis,black porous alumina ceramics were prepared by gel injection molding and pressureless sintering.The effects of raw material formula and process parameters on the phase,structure and properties of black porous alumina ceramics were investigated,which provided theoretical and technical support for the preparation of new vacuum cups.Formula exploration respectively adopts four kinds of black pigment first synthesize black color,and then mix black color with base material and sintering assistant after molding pressing sintering two-step sintering method and all raw materials mixed after molding pressing sintering one-step sintering method.The secondary sintering method,in the synthesis of black color,with the increase of Fe₂O₃ content,the chroma value L*decreases first,then increases,and finally decreases again.The chromaticity value L*decreases first and then increases with the increase of CoO content.As the sintering temperature rises from 1200°C to 1350°C,the chromaticity value L*increases.XRD phase analysis shows that the pigment exists in the form of mixed spinel phase.In the experimental range,the chromaticity values of black pigment L*,a*and b*are25.57～30.08,-0.48～-0.21 and-2.13～-1.61,respectively.In the primary sintering method,when Fe₂O₃ is not more than 3.5 wt.%and CoO is not more than 1.25 wt.%,better coloring effect can be achieved.With the increase of sintering temperature,the volume density of black ceramics increases,and the chroma value L*decreases first and then increases.XRD analysis shows that the main phases of black ceramics are alumina and mixed spinel.Within the scope of the experiment,in the raw material formula 91 wt.%Al₂O₃、2 wt.%Ti O₂、0.5 wt.%Si O₂、3.5 wt.%Fe₂O₃、0.5 wt.%CoO、1 wt.%Ni O and 1.5 wt.%Mn O₂.When the sintering process is held at1450°C for 2 h,the chromaticity value of the prepared black ceramic sample is the lowest,with L*30.15,a*1.14 and b*1.89.The raw material for the same formula respectively by using two step sintering process and preparation step sintering,black pottery and porcelain,the comparison results show that the sample preparation step sintering,black alumina ceramic chromaticity values of L*are lower than those of two step sintering,the preparation of samples,this is because the two step sintering,the first step in the preparation of black pigment composition restructuring happened in sintering again.The amount of black spinel phase is reduced.Black porous alumina ceramics were prepared by gel injection molding and one-time sintering process on the basis of formula exploration.The results show that when the content of sintering aids is 4 wt.%and 6 wt.%,the color value L*of porous ceramics is the lowest.With the increase of pigment content,the chromaticity value L*decreases obviously and the color of porous ceramics gradually deepened.With the increase of sintering temperature or holding time,the porosity of porous ceramics decreases,the compressive strength increases,and the chroma value L*decreases.In the experimental range,the raw material formula was 60 wt.%Al₂O₃、3.2 wt.%Ti O₂、0.8 wt.%Si O₂、10.4 wt.%Fe₂O₃、2.76 wt.%CoO、5.52 wt.%Ni O and 17.32 wt.%Mn O₂.When the sintering process is held at 1250°C for 3 h,the porous black alumina ceramics have the best comprehensive properties,the porosity is 40.6%,the volume density is 2.38 g?cm^-3,the compressive strength is 118 MPa,the chromaticity values of L*,a*and b*are 24.87,2.65 and 4.99,respectively,and the pore size is between 1μm and 4μm.Meet the performance requirements of new vacuum sucker material.