Effects of metal binder on the microstructure and mechanical properties of Al2O3-based micro-nanocomposite ceramic tool material

The Al_2O_3-（W,Ti）C composites with Ni and Mo additions varying from 0vol% to 12vol% were prepared via hot pressing sintering under 30 MPa. The microstructure was investigated via X-ray diffraction（XRD） and scanning electron microscopy（SEM） equipped with energy dispersive spectrometry（EDS）. Mechanical properties such as flexural strength, fracture toughness, and Vickers hardness were also measured. Results show that the main phases A12O3 and（W,Ti）C were detected by XRD. Compound Mo Ni also existed in sintered nanocomposites. The fracture modes of the nanocomposites were both intergranular and transgranular fractures. The plastic deformation of metal particles and crack bridging were the main toughening mechanisms. The maximum flexural strength and fracture toughness were obtained for 9vol% and 12vol% additions of Ni and Mo, respectively. The hardness of the composites reduced gradually with increasing content of metals Ni and Mo.

DLP printing of BT/HA nanocomposite ceramic scaffolds using low refractive index BT crystals

Biological piezoelectric materials have significant potential for bone repair and energy harvesting owing to their excellent biocompatibility and piezoelectric effect.The BaTiO_(3)/Ca_(10)(PO_(4))_(6)(OH)_(2)(BT/HA)composite material is an outstanding representative of biological piezoelectric materials,which has not been individually designed using digital light processing(DLP)3D printing because of the large difference in the refractive index of its components.Therefore,in this work,double-sided-tooth plate-like BT crystals with high curvature were prepared via a hydrothermal process,and BT/HA ceramic slurries were grinded out using dispersed intermittent ball milling scheme,and BT/HA nanocomposite ceramic scaffolds were fabricated by DLP 3D printing technology.The nanostructure,dielectric properties,and piezoelectric energy harvesting performance of the BT/HA nanocomposite ceramic scaffolds were evaluated.The influences of different morphologies and contents for BT on the piezoelectric potential and stress distribution were analyzed based on a multi-physics coupling finite element simulation.The cell proliferation and adhesion abilities were investigated also.The BT/HA nanocomposite ceramic scaffolds present excellent dielectric properties,cell proliferation and adhesion abilities,and an open circuit voltage of 8 V during piezoelectric energy harvesting.The material properties and multi-physics coupling finite element analysis imply that the double-sided-tooth plate-like BT plays an important role for the fastness structure and electric field distribution in the BT/HA nanocomposite.Thus,this work provides a strategy for the application of the customized BT/HA nanocomposite ceramic scaffolds in new-generation orthopedic implants and biological energy harvesting.

Laser sintering of carbon nanotube-reinforced ceramic nanocomposites

The fabrication of carbon nanotube(CNT)-reinforced ceramic nanocomposites through laser sintering has been rarely studied,and the fabrication feasibility has been rarely tested.Laser sintering is a flexible,localized and high-precision process,which can also potentially produce coatings or parts with complicated shapes and/or spatially controlled compositions.Therefore,compared with other technologies laser sintering has its own advantages.Experimental investigations reported in this paper have confirmed the feasibility of fabricating CNT-reinforced ceramic nanocomposites through laser sintering of ceramic nanoparticles and CNTs.The studies show that laser sintering can induce the agglomeration of ceramic nanoparticles into a relatively more continuous ceramic phase,and during the sintering process CNTs are well preserved without any obvious quality degradation,and they are also bonded with the ceramic phase after laser sintering.

Hard and tough novel high-pressure γ-Si_(3)N_(4)/Hf_(3)N_(4) ceramic nanocomposites

Cubic silicon nitride(-Si_(3)N_(4))is superhard and one of the hardest materials after diamond and cubic boron nitride(cBN),but has higher thermal stability in an oxidizing environment than diamond,making it a competitive candidate for technological applications in harsh conditions(e.g.,drill head and abrasives).Here,we report the high-pressure synthesis and characterization of the structural and mechanical properties of a γ-Si_(3)N_(4)/Hf_(3)N_(4) ceramic nanocomposite derived from single-phase amorphous silicon(Si)-hafnium(Hf)-nitrogen(N)precursor.The synthesis of the-Si_(3)N_(4)/Hf_(3)N_(4) nanocomposite is performed at~20 GPa and ca.1500 ℃ in a large volume multi anvil press.The structural evolution of the amorphous precursor and its crystallization to-Si_(3)N_(4)/Hf_(3)N_(4) nanocomposites under high pressures is assessed by the in situ synchrotron energy-dispersive X-ray diffraction(ED-XRD)measurements at~19.5 GPa in the temperature range of ca.1000-1900℃.The fracture toughness(K_(IC))of the two-phase nanocomposite amounts~6/6.9 MPa·m^(1/2) and is about 2 times that of single-phaseγ-Si_(3)N_(4),while its hardness of ca.30 GPa remains high.This work provides a reliable and feasible route for the synthesis of advanced hard and tough-Si_(3)N_(4)-based nanocomposites with excellent thermal stabililty.