Preparation On Micro/Nano-diamond Tools Bonded With Ceramic Abrasive By Polymer Network Sol-gel Method

The surface of diamond powder prepared by mechanical crushing method has lots of defects.Especially nanodiamond?ND?,which has high surface activity,is easy to aggregate.However,NDs are expected to be dispersed stably in multicomponent inorganic salt solution when we prepared ultra-precision grinding tool by the polyacrylamide gel?P-G?method.Therefore,the method of sol-gel method?S-G?was applied to coat diamond?²8 ?m and 100²50 nm?on the surface with TiO₂ in this study,which could make up the surface defects of diamond and improve the suspension dispersion of ND,then prepare the ultra-precision grinding tool by the P-G method.In this study,the microdiamond coated with TiO₂?diamond/TiO₂?were prepared by the S-G method and the effects of the content of PVP and different catalysts on the coating were investigated.Then,the surface of ND was coated with TiO₂?ND/TiO₂?in batch processing by the method of S-G assisted with ultrasonic.A field emission scanning electron microscope?FESEM?,a high resolution transmission electron microscope?HRTEM?and an X-ray diffractometer?XRD?were performed to characterize the morphology and the existing form of TiO₂ coating layer.In addition,the thermo gravimetry-Differential Scanning Calorimetry?TG-DSC?was deployed to analyze the anti-oxidation resistance of the diamond/TiO₂ composites.The experimental results show that under the comprehensive control of ammonia and acetyl acetone,when the ratio of m?PVP?and m?diamond?was 2:1,the coating layers are comprised of equigranular particles of TiO₂ with approximate 20 nm.The oxidation temperature of diamond/TiO₂ composites increase to around 950 °C,which is 300 °C higher than that of the pristine diamond.What is more,the batch preparation of ND/TiO₂ by the S-G method assisted with ultrasonic was realized,and the concentration of ND increased to 10 g/L.Liquid phase method was applied to confirm a kind of ceramic bond formula with low sintering temperature,and the P-G method was used to prepare the ceramic bond,thereafter,ND/SiO₂ and ND/TiO₂ were to added into ceramic bond respectively to prepare the ultraprecision grinding tool.The thermal decomposition of gel,the disperse uniformity of ND/SiO₂ and ND/TiO₂ in the network gel,the microstructure and phase composition of sintered body were characterized by TG-DSC,FESEM and XRD;then the bending strength and porosity of sintered body were measured according to the three points bending method and the Archimedes drainage method.The experimental results show that: when the ratio of m?Na₂O?:m?B₂O₃?:m?Al₂O₃?:m?SiO₂?were 1.1:1.2:1:7.9,the ceramic bond has excellent performance,which its gel powder prepared by P-G method calcined under 520 °C could obtaine ceramic bond with high purity and good dispersancy.And the sintering temperature of the ceramic bond is 650 °C,and the bending strength is 75.1 MPa,nearly 28.6% higher than that of liquid phase method.And the thermal expansion coefficient of the sintered bond is 6.36×10-6/°C.When the diamond concentration increased from 25% to 100% to prepare abrasive sample by P-G method,the ND/SiO₂ existed as a single particle diamond and dispersed uniformly in the gel,however ND/TiO₂ took on a slight agglomeration of about 0.5¹ ?m in size in the gel and the dispersing effect was a bit poor than that of ND/SiO₂.The sintering temperature of ND/SiO₂-ceramic bond sintered body are in a range of 670⁷20 °C,the bendingl strength of that are in a range of 66.4⁸7.6 MPa,and the porosity were in a range of 10.2%²2.4%.The sintering temperature of ND/TiO₂-ceramic bond sintered body are in a range of 660⁷00 °C,the bending strength of that are in a range of 78.1⁹6.9 MPa,and the porosity are in a range of 7.3%¹7.9%.