Da Hu,Jiayun Deng,Jiabin Lu,Qiusheng Yan,Canlin Du,Jiyang Cao
Magnetorheological elastomers (MREs) are widely used in vibration control due to their excellent magneto-controlled mechanical properties. In this research, polyurethane-based MRE polishing pads were prepared and used for the polishing of single-crystal SiC to investigate the magneto-controlled mechanical properties, the magneto-polishing effect, and the mechanism of action thereof. The results show that the pre-structuring process is affected by parameters such as mass fraction and particle size of magnetic particles in MREs and curing magnetic field strength, different chain strings that demonstrate different magnetorheological effects are formed. The greater the mass fraction of magnetic particles and curing magnetic field strength, the more the MREs exhibit magnetorheological effects, especially so when the magnetic particles size of 3 μm. A series of 90 min polishing experiments on single-crystal SiC with original surface roughness (Ra) 80 nm were conducted using an MRE pad. The results indicate that with the increase of polishing magnetic field strengths, the shear modulus of MRE polishing pads increases, the material removal rate (MRR) of the polishing process increases and Ra decreases. As the magnetic field strength is increased from 0 mT to 335 mT, the shear modulus is increased from 1.392 MPa to 1.825 MPa (an increase of 31.1%), while MRR is increased from 706.3 nm h−1 to 835.3 nm h−1 (an increase of 18.3%), Ra is decreased from 19.92 nm to 3.62 nm (an improvement in surface quality of 81.8%). The results show that the increase of the polishing magnetic field strengths changes the material modulus of the MRE polishing pads, which cause the decreases in the compressive and shear elastic deformation of the abrasive grains on the elastic substrate. This increases the positive pressure of the abrasive grains on the SiC wafer, which enhances the material-removal ability of the SiC wafer, thereby improving the surface quality of the wafer.
In photocatalytic-assisted magnetorheological polishing(PMRP), both the opacity of the magnetorheological fluid and the non-magnetic properties of the photocatalyst limit the processing efficiency and quality of SiC wafers. In this paper, the magnetorheological fluid is prepared by using photocatalysts with different physical phases(liquid/solid) and properties(magnetic/non-magnetic), and then the friction chemical mechanism is carried out on SiC. The results show that the transmittance of the magnetorheological fluid and the distribution state of the photocatalyst synergistically cooperate to control the chemical oxidation rate of single-crystal SiC. When using magnetic particles with photocatalytic coatings for processing, the photocatalytic reaction spots can be effectively constrained and the SiC oxidation efficiency can be improved.
Da Hu,Jiabin Lu,Jiayun Deng,Qiusheng Yan,Haotian Long,Yingrong Luo
Magnetic particles (Fe 3 O 4 /CIP) in magnetorheological elastomer (MRE) were used as solid-phase catalysts in the heterogeneous Fenton reaction for chemical mechanical polishing (CMP) of single-crystal SiC. The polishing effect and polishing mechanism were investigated by experiments and polishing debris analysis. The results show that when using H 2 O 2 polishing solution the material removal rate (MRR) was higher and the surface roughness (Ra) was lower at all stages of polishing than using deionized water polishing solution. The MRRs when polishing for 60 min with the deionized water and the H 2 O 2 polishing debris were, respectively, 636.94 nm/h and 1194.27 nm/h (an increase by 87.5%), and the corresponding Ra values were, respectively, 12.445 nm and 4.420 nm (a decrease by 64.5%). From the analysis of the polishing debris after 60 min of polishing, it was found that the H 2 O 2 polishing solution was polished with laminated loose chips, and the main elements of the chips were C, O, and Si, with O element accounting for 38.585 wt%. This indicates that a chemical reaction has occurred on the SiC surface during polishing, generating low hardness and low binding strength SiO 2 , and thus resulting in increased material removal; this phenomenon is confirmed by the profile morphology of SiC wafer by fixed-point polishing. It is shown that the use of Fe 3 O 4 /CIP in MRE as a solid-phase catalyst for the heterogeneous Fenton reaction of polishing SiC can substantially increase the material removal capacity of MRE polishing pads and improve the polishing quality at the same time.
危险品化学品经营许可证（带存储）