Thin Ceramic Plate Research Articles

Critical evaluation of SEVNP-method to measure fracture toughness of ceramic thin plates

The fracture toughness of ceramic substrates made of alumina, ZTA and silicon nitride was determined using the single edge V-notched plate method. In order to make a statement about the measurement precision, not only 5, as required by the standard, but 30 specimens per material type were tested. In addition, a much more practical and less error-prone holding and testing device for the ceramic plates was used, which is presented in the paper. For all materials, including the comparatively fine-grained ZTA, the material-typical KIc values could be determined. However, the range of variation of the measured values is comparatively high with coefficients of variance up to 7.8 %. It is shown that a standard-compliant test on Al2O3 substrates can exhibit a fluctuation range of 0.5 MPa m0.5 without the material showing any differences. It is important to be aware of this when using the method. Especially for quality assurance, where deviations in the range of a few tenths of MPa∙m0.5 are considered problematic, the method should therefore be regarded as critical. An increase in the number of specimens should be considered, as well as the inclusion of a statement on the precision of the measurement method in the standard.

REDUCTION OF CRACK FORMATION DURING ABRASIVE TREATMENT WITH DIAMOND PASTES OF SILICON CARBIDE SEMICONDUCTOR PLATES

The results of diamond-abrasive treatment of the reverse side of silicon carbide semiconductor plates of polytypes 4H and 6H are presented. Dimensions of surface microcracks of ceramic plates after abrasive treatment with pastes with diamond powder of different grain size are investigated, and also relationship between length of surface microcrack and rate of material removal depending on technological modes of diamond-abrasive treatment is established. As a result, a new method of single-sided abrasion treatment of thin ceramic plates is proposed, which ensures reduction of crack formation.

Properties and evolutions of high-performance porcelain thin ceramic plates enhanced by multi-phase microstructure derived from sustainable smoky quartz tailings

In the case of the shortages of high-quality ceramic mineral resources, there are enormous challenges in developing high-performance ceramic materials with low-quality tailings. As recently discovered rare-earth mineral tailings, smoky quartz tailings are regarded as cheap raw materials for ceramic manufactures, but not efficiently utilized in the field of high-performance thin ceramic plates. To deeply explore the application possibilities, recycled smoky quartz tailings treated by thermal activation are used as sustainable raw materials to prepare high-performance porcelain thin ceramic plates. The porcelain thin ceramic plates sintered at 1200 °C for 2 h have the best mechanical performance, the bulk density, bending strength and compressive strength respectively reach the maximal value of 2.86 g/cm3, 118.79 MPa, and 1126.35 MPa. It is found that smoky quartz tailings can promote the formation process of liquid phases that act as fillers for micropores to improve the matrix density at the sintering stage. The excellent mechanical properties of ceramic plates benefit from multi phases and their dense microstructure, high-strength corundum, and in-situ labradorite are beneficial to preventing brittle fracture behaviors and improving the mechanical properties. Microcracks deflection, dispersed particle enhancement, transgranular fracture and intergranular fracture are proved to be the main mechanical mechanisms of porcelain thin ceramic plates. This research can provide ideas for recycling low-quality mineral tailings in ceramic manufactures in the future.

Mechanical properties of large-sized thin architectural ceramic plate enhanced by alumina fibres and in situ mullite whiskers

The fibres reinforced thin architectural ceramic plates of 900?1800?2.5mm with excellent mechanical properties were prepared by fast-sintering method using a controllable fibre dispersion process. The effects of ball-milling time on dispersity, average length-to-diameter ratio and microstructure of alumina fibres were investigated. Meanwhile, the effects of alumina fibre contents on the bulk density, water absorption, phase transformation and microstructure of the thin ceramic plate were researched. It was found that the two-step ball-milling process can effectively control the average length-to-diameter ratio of alumina fibres, achieving a good dispersion mixture of fibres and ceramic powders. Ceramics bulk density and bending strength increase with fibre contents rise from 0 to 5 wt.% and then decrease with further fibre content addition from 5 to 15wt.%. The in situ formed mullite whiskers via fast-sintering method are beneficial for protecting fibres and fibre/matrix interfaces. The maximum value of bending strength and fracture toughness reach 147MPa for 5 wt.% fibre contents and 2.6MPa?m1/2 for 9 wt.%fibre contents, corresponding to the strengthening of alumina fibres and the formation of mullite whiskers in fibre/matrix interfaces and matrix via fast-sintering process.

Size effect on heat conduction and associate thermal fracture behavior of thin ceramic plates

Thermal barrier materials used in gas-turbine engines and aerospace vehicles have to resist large thermal gradients or high heat fluxes. The existence of high temperature gradient results in nonlocal effect of heat conduction, especially in very small time and space scale, the size effect of heat conduction is significant. In this work, a nonlocal dual-phase-lag heat conduction model is adopted to analyze the thermal shock fracture problem of thin cracked plates under sudden thermal shock. By using Laplace transform and inverse transform, the temperature field and the thermal stress field are obtained first. Then through the principle of superposition, the formulation results in a mode I crack problem. In the numerical part, the effects of different heat conduction models, thermal nonlocal parameters, and crack geometry parameters on the transient responses are discussed. By comparison analysis, the results show that taking the size effect into account is crucial in the assessment of thermal shock fracture of ceramic plates at micro/nano scale. The stress intensity factor first increases and then decreases with the increase of crack geometry parameters, indicating that the cracked plate exhibits crack growth resistance behaviour.

Pre-crack and Fracture Toughness Evaluation of Ceramic Thin Plates

Pre-crack and Fracture Toughness Evaluation of Ceramic Thin Plates

Drying-Induced Strain-Stress and Deformation of Thin Ceramic Plate

Ceramic thin plates are applied to several industrial purposes including electronic materials and sensors. Drying-induced shrinkage and strain-stress formation of a ceramic thin plate were studied experimentally and theoretically. A kaolin thin plate molded into 10 mm × 30 mm × 1 mm was dried in a hot air stream, and the drying characteristics and deformation were examined. Modeling was also performed to predict the behavior. Heat and moisture transfer conservation equations and constitution equations based on viscoelastic strain-stress were simultaneously solved by a finite element method. A test piece of the thin plate was warped when only one side of the plate was dried, while it was almost flat when both sides were dried. The behaviors of drying and deformation were predicted with a reasonable agreement by the modeling. Parametric analyses by the modeling revealed that the drying conditions with faster drying rate in the beginning period resulted in formation of greater maximum principal stress, and drying on only one side of the plate induced stronger tensile stress in falling rate period than that with both sides drying. The larger thickness of the plate influenced the formation of significantly greater tensile stress but affected maximum compressive stress only a little.

Round‐robin exercise on the three‐ and four‐point flexural strength of thin ceramic plates for power modules

AbstractRound‐robin exercises on three‐ and four‐point flexural tests were successfully conducted to evaluate the fracture strength of Si3N4, Al2O3, and AlN thin plates for power modules. A 0.64 mm × 12 mm × 40 mm test specimen was loaded in three‐point flexure with a major span of 30 mm or was loaded in four‐point flexure with a major/minor span of 30/10 mm. For a 0.32 mm × 12 mm × 20 mm test specimen, both major and minor spans were halved. All test specimens were loaded in a fully articulated fixture provided by the test organizer. Reasonable consistencies in the resultant flexural strength were obtained between laboratories, indicating our new test condition for three‐ and four‐point bending of thin ceramic plates is satisfactory for reliable measurement of the flexural strength.

Avoiding Processing Cracks in Thin Ceramic Plates by Optimization of Sand Blasting Conditions

Avoiding Processing Cracks in Thin Ceramic Plates by Optimization of Sand Blasting Conditions

Measurements of fracture toughness of ceramic thin plates through single-edge V-notch plate method

Round-robin tests on the single-edge V-notch plate (SEVNP) method were conducted successfully to evaluate the fracture toughness of Al2O3, AlN and Si3N4 thin plates whose grain sizes were more than 2μm. A straight-through notch was introduced into a plate with the thickness of 0.32 or 0.64mm and sharpened by means of razor blade with diamond pasts to prepare a V notch. The V-notched thin specimens were loaded in a special 3pt-fixture with a vertical thin slit to determine the flexural strength. Reasonable consistencies in the resultant fracture toughness were attained between laboratories regardless of the thickness of ceramic plate, indicating the SEVNP method can be an effective test technique for measurements of fracture toughness of the ceramic thin plates.

Toughening of thin ceramic plates using bioinspired surface patterns

High-performance natural materials such as bone, teeth or mollusk shells contain a large volume fraction of minerals to generate stiffness and hardness. They are also packed with weak interfaces, which generate nonlinear deformations and channel cracks into powerful toughening configurations. As a result, these natural materials achieve simultaneous stiffness, hardness and toughness, which are properties which are mutually exclusive in engineering materials. Following these concepts, we have engraved trenches with controlled patterns and depth in thin plates of aluminum oxide. The trenches can guide propagating cracks, which we use to implement toughening mechanisms and unusual deformation mechanisms. We present fracture results on samples with transverse interfaces and sinusoidal interfaces. We also explore interlocking-jigsaw like interfaces, which dissipate the most energy and produce the highest toughness. These interfaces also profoundly change the way the material deform in tension, by introducing controlled non-linear deformations accompanied with geometric hardening and frictional pullout, in an otherwise all-brittle material.

Round-robin test on the fracture toughness of ceramic thin plates through modified single edge-precracked plate method

Round-robin tests on the modified single edge-precracked plate method were conducted successfully to determine the fracture toughness of Si3N4, AlN and Al2O3 thin plates. A small, thin single edge notched plate with the thickness of 0.32 or 0.64mm was bonded on one side of a brass beam and the assembly was loaded in a three-point fixture to introduce the precrack. A special 3pt-bending fixture with a vertical slit was employed for the strength test. Good matches in the resultant fracture toughness were obtained between laboratories regardless of the thickness of ceramic plate, confirming the reliability of the new method.

201 薄板セラミックスの破壊じん性とR曲線の評価(機械材料I)

201 薄板セラミックスの破壊じん性とR曲線の評価(機械材料I)

Evaluation of fracture toughness of ceramic thin plates through modified single edge-precracked plate method

In order to evaluate fracture toughness of thin plates of aluminum nitrides and silicon nitrides, a small, thin single edge notched plate with the thickness of 0.32 or 0.64 mm was glued on one side of a brass beam and the assembly was deformed in three-point bending to introduce the precrack. The flexural strength of the precracked specimen was measured using a special 3pt-bending fixture. The resultant fracture toughness was almost identical to those obtained for the standard-sized specimens.

Characteristics analysis and parametric study of a thermoelectric generator by considering variable material properties and heat losses

The output power and conversion efficiency of the thermoelectric generator (TEG) are closely related to not only the materials properties but also the geometric structure. This paper developed a multi-physics, steady-state, and three-dimensional numerical TEG model to investigate the TEG performance, and then the model is compared with the classical thermal resistance model. Bismuth-telluride are used as p- and n-type materials. The comparison reveals that the assumption of constant material properties leads to underestimated inner electrical resistance, and overestimated thermal conductance and Seebeck coefficient, so that the thermal resistance model predicts unrealistically high performance than the present model. The results also indicate that when heat losses exist between the TEG and the ambient, although the output power is slightly elevated, the conversion efficiency is significantly reduced, hence, improvement of the heat insulation effect is critically important for high-temperature TEGs. Furthermore, the TEG geometry also affects its performance significantly: usage of thin ceramic plates increases the junction temperature difference, and hence enhances the TEG performance; there are two optimal leg lengths which correspond to the maximum output power and the maximum conversion efficiency, respectively; when heat losses are not ignorable, a large semiconductor cross-sectional area remarkably reduces the ratio of the heat liberated to the ambient to the heat absorbed from the high-temperature heat source, and hence improves the conversion efficiency.

Evaluation of Thermal Conductive Resistance at Organic–Inorganic Interface and Effect of Interfaces on Thermal Conductivity of Composite Materials

The effect of organic–inorganic interfaces on the thermal conductivity of composite materials was studied by evaluating thermal conductive resistance at the organic–inorganic interfaces experimentally. Polymer layers were sandwiched between thin ceramic plates to produce multilayer stacked samples. Through the comparison between the thermal conductivities of the multilayer stacked materials and those of single component materials for both polymers and ceramics, the thermal resistance at the interface between a polymer and a ceramic plate was evaluated. The results suggest that the contribution of thermal resistance becomes significant for actual composite materials because of the increase in the number of interfaces. The results also demonstrate that organic modifications of an inorganic surface could effectively reduce interfacial thermal resistance. The control of interfaces seems to be effective for improving the thermal conduction property of composite materials.

Low-voltage pulsed plasma discharges inside water using a bubble self-generating parallel plate electrode with a porous ceramic

Characteristics of pulsed bubbles discharges in water were investigated using parallel punched plate electrodes with a porous thin ceramic plate inserted between two metal plates. The micro-bubbles were generated just beneath the porous ceramic plate by flowing gas through it. The transition from spiky dielectric barrier discharges to pulsed glow discharges enables efficient bubble discharges at a relatively low voltage of 1.8 ∼ 4.0 kV of the 5 kHz square-waves with a pulse-width of about 750 ns. With 80% Ar and 20% O2 mixture gas at 4.0 kV, the 50 mg/l Indigo Carmine aqueous solution was efficiently decolorized within about 3 min.

Dynamic response of metals under high-intensity pulsed ion beam irradiation for surface modification

A piezoelectric transducer based on lead–zirconte–titanate (PZT) piezoelectric ceramic thin plate was applied to characterize the stress waves in titanium targets under high-intensity pulsed ion beam (HIPIB) irradiation at a peak accelerating voltage of 350 kV and an ion current density up to 400 A/cm 2 with pulse duration of about 150 ns. The magnitude of recorded stress wave signals was increased along with the irradiation intensity, presenting a slow growth with a value below 100 V in the range of 200–300 A/cm 2, and then a rapid increase of about four times up to 400 A/cm 2. The measured stress waves were explained by space–time diagram analysis. The generation and propagation of the stress wave can be attributed to the coupled thermal–dynamic effects during HIPIB irradiation onto metallic targets, where the thermal shock due to ultra-fast heating/cooling process and the recoil impulse due to ablation process have a combined contribution to the induced stress waves, dependent on the irradiation intensity. It is indicated that a fast attenuation of stress wave proceeded during its propagation from the irradiated surface to the target/PZT interface. The large amount of energy delivered by the stress wave effectively converted and dissipated into plastic deformation and/or defects formation in target materials. The dynamic response of metallic materials under HIPIB irradiation accounts for the effective surface modification of metals and alloys into a depth well beyond the ion range.

Measurement of Flexoelectric Effect in Lead Zirconate Titanate Ceramics

Lead zirconate titanate (PZT) ceramics is usually used as a piezoelectric material. However it has characteristics of not only piezoelectricity but also flexoelectricity. Piezoelectricity is a phenomenon that electric polarization is induced by strain, and flexoelectricity is the one that the polarization is induced by strain gradient. In this study, flexoelectricity in poled soft PZT ceramics is measured. In order to eliminate influence of piezoelectricity, PZT ceramic thin plates are subjected pure bending using four-point bending experimental mechanism. Strain gradient along the direction of thickness in the plate is caused by the bending motion. Electric charge between two electrodes which is set on the center of the plate surface is measured under quasi-static sinusoidal load. Even though the polarization for piezoelectric effect is eliminated by the experimental setup, the influence of piezoelectric effect still remains since polarization by piezoelectricity is much larger than the one by flexoelectricity. So the influence of piezoelectricity is eliminated using qualitative difference between piezoelectricity and flexoelectricity for poling direction. Eventually, flexoelectric coefficient of the order of 10-5 C/m is measured.

Stress wave attenuation in ceramic plates

Studies on planar longitudinal stress wave attenuation in thin ceramic plates are presented using a wave tracking algorithm. The results are also experimentally validated. Ceramic plates consist of grains and grain boundaries. Elastic modulus and density of the grain boundaries are less than those of the grains. When the planar longitudinal stress wave encounters an interface between the grain and the grain boundary, reflection and transmission of the incident stress wave take place because of the impedance mismatch at the interface. It is observed that this leads to attenuation in stress wave intensity. This behavior is represented by stress wave attenuation coefficient. It is observed that the stress wave attenuation coefficient is a material property.