Alumina Matrix Ceramic Materials Research Articles

Effect of load on friction and wear behaviors of alumina matrix ceramic guideway materials

According to the tensile crack model, a simple model for tribological behaviors of diopside/AlTiB toughened alumina matrix ceramic guideway materials, predicting the relationship between load and wear rate, was presented. 45# steel ring was used as the counterpart. Mechanical properties and wear properties of the guideway materials under different loads were investigated. SEM micrographs of wear tracks on typical specimens were studied. Results showed that the experimental data described in this paper were in accordance with the theoretical prediction. Introduction of diopside and AlTiB master alloys in alumina matrix ceramic guideway materials improved their mechanical properties, friction and wear properties. The wear rate of pure alumina was in the order of 10−15 m3/N·m while that of guideway materials toughened by diopside and AlTiB master alloys was in the order of 10−16 m3/N·m. The wear mechanisms of pure alumina may be brittle fracture and grain pull-out. The dominant wear mechanisms of alumina matrix ceramic guideway materials toughened by diopside and AlTiB master alloys may be mechanical interlocking and plastic deformation combined with a little micro-fracture and grain pull-out.

Hot pressing of Al2O3 matrix ceramic materials improved by diopside additive

Abstract As a sintering aid, diopside was introduced into alumina matrix ceramic materials. Composites were fabricated using transient liquid phase sintering, during which new phases such as mullite, anorthite and CaO · 6Al2O3 were produced by the chemical reactions taking place between alumina and diopside. The densification rate of the composites as a function of diopside volume content is discussed. The hardness, fracture toughness and bending strength of the composites were tested. Meanwhile, the effects of diopside content, grain size and interface on mechanical properties and fracture mechanism of alumina matrix ceramic materials are analyzed and discussed.

Addition of rare earth and diopside to improve performances of alumina matrix ceramic materials

In the present work, mixed rare earth and diopside were simultaneously introduced in alumina matrix ceramic materials. Composites were fabricated by hot press sintering, during which liquid phase, leading to interface reactions between alumina matrix and additives, was formed. Hardness, fracture toughness and bending strength of the composites were measured. Microstructure observations on fracture surfaces of alumina matrix ceramic materials were analysed. Results showed that diopside, as a sintering assistant, could prompt the formation of transient liquid phase as well as carbides and nitrides of rare earth elements and thus contributed to improve the mechanical properties of alumina matrix ceramic materials.

Microstructures and sintering kinetics of pressureless sintered alumina doped with diopside and AlTiB

In the present work, diopside and AlTiB were simultaneously introduced in alumina using pressureless sintering. Microstructures of the composites were observed at a given temperature of 1520°C and different holding time. Sintering densification process of the composites was studied. Experiments were performed in the temperature at equal increments: 1420, 1520, 1620 and 1720°C, and with four holding times, i.e. 100, 140, 180 and 220min. The apparent activation energies of 17.7–28.8kJ/mol for alumina matrix ceramic materials were calculated by least squares. The sintering kinetic equations were deduced. Results showed that the sintering of monolithic alumina was controlled by volume diffusion, and that of alumina matrix ceramic materials doped with diopside and AlTiB was controlled by grain boundary diffusion and volume diffusion.

Hetero-modulus alumina matrix nanoceramics and CMCs with extreme dynamic strength

Applying the well-known alumina powders for matrix, different oxide and non-oxide ceramic submicron and nano-particles as additive materials, and investigating the impact of nitrogen atmosphere on sintering; the authors successfully developed new hetero-modulus alumina matrix ceramic composite materials, reinforced with submicron and nanoparticles of α-Si3N4 β-Si3N4, Si2ON2, SiAlON and AlN. Thanks to the new compacting technology with high speed flying punches in vacuumed N2 atmosphere developed by authors, phase transformation of α-Si3N4 and β-Si3N4 into cubic c-Si3N4 can be observed, creating so-called Si3N4-diamond submicron and nanoparticles in alumina matrix. The α-Si3N4, β-Si3N4, Si2ON2, SiAlON, AlN and c-Si3N4 diamond submicron and nanoparticles reinforced alumina matrix hetero-modulus nanoceramics have excellent mechanical properties and extreme dynamic strength. The dynamic strength was tested through collision with high density metallic flying bodies, with speed higher than 900 m/sec. Analytical methods applied in this research were laser granulometry, scanning electron microscopy, X-ray diffraction and energy dispersive spectrometry. Digital image analysis was applied to microscopy results, to enhance the results of transformation.

ChemInform Abstract: Addition of Zr—O—B Compounds to Improve the Performances of Alumina Matrix Ceramic Materials

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Effect of diopside addition on sintering and mechanical properties of alumina

In this paper, diopside was introduced in alumina as a sintering aid and fine structural alumina matrix ceramic materials were fabricated by pressureless sintering. The relative density, hardness, fracture toughness and bending strength of the new fabricated composites were measured. Tribological tests were carried out at a given rotation speed of 160 rpm and in a normal load ranged from 50 to 200 N. The experiment results show that the introduction of diopside can enhance densification rate, which may contribute to the improvement in mechanical properties and result in enhanced wear resistances. The effects of diopside on mechanical properties and microstructures of fine structural alumina matrix ceramic materials were analyzed and discussed.

Pressureless sintering of alumina matrix ceramic materials improved by Al–Ti–B master alloys and diopside

Al–Ti–B master alloys and diopside are simultaneously introduced in alumina matrix ceramic materials as sintering aids. Fine structural alumina matrix ceramic materials are fabricated by pressureless sintering during which liquid phase, leading to interface reactions between alumina matrix and additives, is formed. Hardness, fracture toughness and bending strength of the composites are measured. The effects of diopside on mechanical properties and fracture mechanism of fine structural alumina matrix ceramic materials are analyzed together with the microstructure observations on fracture surfaces, the polished surfaces and the indentation cracks.

Research on toughening mechanisms of alumina matrix ceramic composite materials improved by rare earth additive

Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It was indicated that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550 °C and 28 MPa for 30 min were improved evidently. Besides mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistants, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All of the above were beneficial for improving the mechanical properties of alumina matrix ceramic composites.

Tribological properties of pressureless sintered advanced alumina matrix ceramic materials improved by Al–Ti–B and diopside

Al–Ti–B master alloys and diopside were incorporated into alumina matrix and advanced alumina matrix ceramic materials were fabricated by pressureless sintering technology. The mechanical properties of this new composite as well as its wear behaviours, coupled with carbon steel ring in unlubricated conditions at room temperature, were investigated systemically. SEM technology was adopted to observe the worn surfaces of specimens and wear mechanisms were simultaneously discussed. Analysis of the experimental data and observations on the worn surfaces revealed that the improvement in the wear resistance of the composites might be attributed mainly to the strong toughening effect due to the introduction of Al–Ti–B master alloys and diopside in the alumina matrix.

Toughening mechanism of alumina-matrix ceramic composites with the addition of AlTiC master alloys and ZrO2

Abstract Titanium carbide and aluminium are introduced in alumina matrix in the form of AlTiC, which is a kind of master alloy. Alumina-matrix ceramic composites are prepared by using transient liquid phase and hot-press sintering. Significant improvements in mechanical properties have been attained due to the good toughening effect of AlTiC master alloys and ZrO 2 . The microstructures and toughening mechanisms of the fabricated alumina-matrix ceramic materials are analysed using a scanning electron microscope, a transmission electron microscopy and an electron probe microanalysis, respectively. Results show that the microstructures of “intracrystalline shape” and “intercrystalline shape” are formed and “sublattice” exists in the composites, which may extend crack path and restrain intracrystalline failure, thus improving the fracture toughness of the composites.

Tribological properties of pressureless sintered alumina matrix ceramic materials improved by diopside

In this paper, diopside was introduced into alumina as a sintering aid and fine structural alumina matrix ceramic materials were fabricated by the technology of pressureless sintering. The relative density, hardness and fracture toughness of the diopside-reinforced composites were investigated. Tribological tests were carried out at a rotation speed ranged from 40 to 160 rpm and in a normal load ranged from 50 to 200 N. SEM technique was employed to observe worn surfaces of the test specimens and wear mechanisms were simultaneously discussed. Analysis of the experimental data and observations on worn surfaces revealed that the improvement in wear resistance of composites may be attributed mainly to the stronger toughening effect due to addition of diopside in alumina matrix.

Fabrication of Al 2O 3/TiB 2/AlN/TiN and Al 2O 3/TiC/AlN composites

Two master alloys as Al-Ti-B and Al-Ti-C were, respectively, introduced in alumina matrix ceramic materials. Composites of Al 2O 3/TiB 2/AlN/TiN and Al 2O 3/TiC/AlN are fabricated by the technology of hot-pressing liquid phase sintering, during which AlN and TiN phases are produced by the chemical reactions taking place among Al, Ti and N 2 (the protective atmosphere). The hardness, fracture toughness and bending strength of the new fabricated composites were tested. The relations of volume content of Al-Ti-B and Al-Ti-C master alloys and mechanical properties of alumina matrix ceramic materials are analyzed. The influences of Al-Ti-B and Al-Ti-C additions were studied by mechanical properties evaluations and microstructural observations. Meanwhile, the expected improvement of mechanical properties compared with pure alumina was indeed observed. The fracture mechanism of alumina matrix ceramic composites was analyzed together with the refining performances of the two master alloys.

Large-scale fine structural alumina matrix ceramic guideway materials improved by diopside and Fe 2O 3

Diopside and Fe 2O 3 were introduced in alumina matrix ceramic materials. Large-scale fine structural alumina matrix ceramic guideway materials were fabricated by the technology of pressureless sintering, during which liquid phase sintering took place and new phases such as 3Al 2O 3·2SiO 2, CaO·Al 2O 3·2SiO 2 and CaO·6Al 2O 3 were produced by the chemical reactions taking place among alumina and the additives. The hardness, the fracture toughness and the bending strength of the guideway products were tested. The influences of diopside and Fe 2O 3 additions were studied by microstructural observations and mechanical properties evaluations. Meanwhile, the expected improvement of mechanical properties compared with pure alumina was indeed observed. The fracture mechanism and porosity of large-scale fine structural alumina matrix ceramic guideway materials were analyzed.

Pressureless sintering of large-scale fine structural alumina matrix ceramic guideway materials

In the present work, diopside is introduced in alumina matrix ceramic materials as a sintering aid. Large-scale fine structural alumina matrix ceramic guideway materials are fabricated by the technology of pressureless sintering, during which transient liquid phase sintering comes into being and new phases such as 3Al 2O 3·2SiO 2, CaO·Al 2O 3·2SiO 2 and CaO·6Al 2O 3 are produced by the chemical reactions taking place among alumina and the additives. The densification rate of the guideway composites as a function of diopside content is discussed. The hardness, the fracture toughness and the bending strength of the guideway products are tested. Meanwhile, the effects of diopside on mechanical properties, fracture mechanism and porosity of large-scale fine structural alumina matrix ceramic guideway materials are analyzed.

Addition of Al–Ti–B master alloys to improve the performances of alumina matrix ceramic materials

In the present work, a new technique to improve the performances of alumina matrix ceramic materials is presented, in which Al, Al 3Ti and TiB 2 are incorporated into alumina matrix ceramic materials in the form of Al–Ti–B master alloys. Composites of Al 2O 3/TiB 2/AlN/TiN are fabricated by the technology of transient liquid phase sintering, during which new phases such as AlN and TiN are produced by the chemical reactions taking place among Al, Ti and N 2 (the protective atmosphere). The densification rate of the composites as a function of Al–Ti–B volume content is discussed. The fundamental properties of the composites such as hardness, fracture toughness and bending strength are examined. The relations of volume content of Al–Ti–B master alloys and mechanical properties of alumina matrix ceramic materials are analyzed. The effects of fracture mechanism on mechanical properties of the composites are researched together with the refining performances of Al–Ti–B master alloys.

Addition of Al–Ti–C master alloys and diopside to improve the performance of alumina matrix ceramic materials

In the present work, Al–Ti–C master alloys and diopside are introduced in alumina matrix ceramic materials. Composites are fabricated by the technology of transient liquid phase sintering, during which new phases such as Al 6Si 2O 13, AlN and CaO·6Al 2O 3 are produced by the chemical reactions taking place among alumina and the additives. The densification rate of the composites as a function of Al–Ti–C volume content is discussed. The hardness, the fracture toughness and the bending strength of the composites are tested. Meanwhile, the effects of additives on mechanical properties and fracture mechanism of alumina matrix ceramic materials are analyzed and discussed together with the refining performances of Al–Ti–C master alloys.

Addition of Al–Ti–C master alloys and ZrO 2 to improve the performance of alumina matrix ceramic materials

A new technique to toughen alumina matrix ceramics is presented, in which Al and TiC are incorporated into the matrix ceramic in the form of Al–Ti–C master alloys, meanwhile ZrO 2 are introduced to Al 2O 3/Al–Ti–C composites. Composites of Al 2O 3/TiC/ZrO 2/AlN and Al 2O 3/TiC/AlN were fabricated by the technology of transient liquid phase sintering, during which new AlN phase was produced by the chemical reactions taking place between Al and N 2 (the protection atmosphere). The toughening effect of Al–Ti–C master alloys on alumina matrix ceramics was researched along with the influence of combination of Al–Ti–C master alloys and ZrO 2. Mechanical properties of the composites were determined and the microstructures were analyzed.