Thermal Expansion Of Ceramics Research Articles

The Synergy Reinforcement Effect of Sm0.85Zn0.15MnO3 and ZrMgMo3O12 on Sm0.85Zn0.15MnO3-ZrMgMo3O12/Al-20Si Composites.

Negative thermal expansion (NTE) ceramics Sm0.85Zn0.15MnO3 (SZMO) and ZrMgMo3O12 (ZMMO) were selected to prepare Sm0.85Zn0.15MnO3-ZrMgMo3O12/Al-20Si (SZMO-ZMMO/Al-20Si) composites using ball milling and vacuum heating-press sintering processes in this study. The synergistic effect of the SZMO and ZMMO NTE ceramic reinforcements on the microstructure, mechanical properties, and coefficient of thermal expansion (CTE) of the composites was investigated. The results show that the processes of ball milling and sintering did not induce the decomposition of SZMO or ZMMO NTE ceramic reinforcements, nor did they promote a reaction between the Al-20Si matrix and SZMO or ZMMO NTE ceramic reinforcements. However, the excessive addition of SZMO and ZMMO NTE ceramics led to their aggregation within the composite. Adding a small amount of SZMO in combination with ZMMO effectively increased hardness and yield strength while reducing CTE in the Al-20Si alloy. The improvement in strength was primarily provided by SZMO, while the inhibition effect on CTE was primarily provided by ZMMO. An evaluation parameter denoted as α was proposed to evaluate the synergy effects of SZMO and ZMMO NTE ceramic reinforcements on the mechanical properties and CTE of the composites. Based on this parameter, among all composites fabricated, adding 2.5 vol% SZMO NTE ceramic and 10 vol% ZMMO NTE ceramic resulted in an optimal balance between CTE and strength for these composites with a compressive yield strength of 349.72 MPa and a CTE of 12.55 × 10-6/K, representing a significant increase in yield strength by 79.20% compared to that of Al-20Si alloy along with a notable reduction in CTE by 26.44%.

Low thermal expansion of high-entropy (ZrMg1−xMnxAlFeCr)0.4Mo1.5W1.5O12 with enhanced mechanical properties

Low thermal expansion (LTE) ceramics are needed to relieve stress in fine devices. Here we adopt high entropy to realise LTE (ZrMgAlFeCr)0.4Mo1.5W1.5O12 with an orthorhombic structure, but presenting poor mechanical properties. To improve the mechanical properties, we increase the compactness of the lattice structure by replacing Mg2+ (ionic radius: 72 p.m.) with Mn2+, which has a larger ionic radius (81 p.m.). As the content of Mn in (ZrMg1−xMnxAlFeCr)0.4Mo1.5W1.5O12 increases, the elastic modulus and compressive strength increase notably owing to the dense microstructure. At x = 0.3, the sample crystallises in the monoclinic phase, and the monoclinic–orthorhombic phase transition temperature increases slightly with an additional increase in the Mn content. Beyond the monoclinic–orthorhombic phase transition, the samples present LTE. The investigation paves a way to realise LTE ceramics with enhanced mechanical properties.

Modeling Wear and Friction Regimes on Ceramic Materials with Positive and Negative Thermal Expansion

Computer modeling of rubbing between two surfaces with microasperities capable of expanding or contracting under conditions of frictional heating (i.e., possessing either positive and negative coefficient of thermal expansion (CTE)) allowed for the identification of wear-and-friction regimes on model ceramic materials. Assuming that no adhesion was involved in the interaction between asperities, two wear regimes—i.e., wear-free and continuous wear—have been revealed in both materials as dependent on the applied normal stress level and sliding velocity. The effect of the normal load on wear rate was similar for both positive and negative thermal expansion ceramics. Sliding velocity has a qualitatively different effect on the wear of materials with either positive or negative thermal expansion. The results indicated that the feasibility of reconstructing wear maps was common for both positive and negative CTE ceramics in terms of dimensionless mechanical and thermophysical characteristics.

Preparation study for the low thermal expansion spodumene/mullite composites

AbstractIn this work, spodumene/mullite ceramics with low thermal expansion were successfully prepared from spodumene, quartz, talc, and clay. The effects of spodumene content and sintering temperature on the mechanical properties of spodumene/mullite ceramics were investigated. The formed phases were then detected by X‐ray diffraction analysis and the microstructures of the sintered bodies were determined by scanning electron microscopy. The interaction effects of the spodumene content and sintering temperature on the apparent porosity and bulk density were studied by response surface methodology. The results demonstrate that an appropriate sintering temperature and spodumene content can promote densification, improve the mechanical properties, and reduce the coefficient of thermal expansion (CTE) of spodumene/mullite ceramics. At the spodumene content of 40 wt.%, the sintering temperature of 1270°C, and the holding time of 90 min, the bending strength was 60.45 MPa, the CTE was 1.73 × 10–6/°C (α[25–650°C] < 2 × 10–6/°C), the bulk density was 2.28 g cm‐3, and the apparent porosity was 0.43%. Therefore, this study was of guiding significance for reducing the production cost of spodumene low thermal expansion ceramics and improving product quality.

Negative and Near-Zero Thermal Expansion in A2M3O12 and Related Ceramic Families: A Review

This review presents the history of materials in the A2M3O12 and related ceramic families, including their unusual thermal expansion and the present understanding of its mechanism, and related factors such as hydroscopicity and the monoclinic to orthorhombic phase transition. Other properties, including thermomechanical, thermal and ionic conduction and optical properties, are presented in terms of current knowledge, challenges and opportunities for applications. One of the largest challenges is the production of monoliths, and various methods for consolidation and sintering are summarized. These ceramics have considerable promise when combined with other materials, and recent advances in such composites are presented. These matters are placed in the context of the potential applications of negative and near-zero thermal expansion ceramics, which still present challenges for future materials researchers.

Ultra-precision finishing of low expansion ceramics by compliant abrasive technologies: A comparative study

Advanced ceramics have many attractive features such as high stability and wear resistance that find broad applications in various fields, e.g. optics, aerospace, etc. However, the accompanying difficult-to-machine property with complex geometry brings great challenges to the commonly used laser machining and rigid wheel based grinding in industry. To achieve optical surface quality with surface roughness below 10 nm Ra, three promising ultra-precision compliant machining technologies using adaptive elastic tools are presented in this paper, including bonnet polishing, compliant pitch polishing and shape adaptive grinding with fine grain size. A comparative study was conducted by machining three different low thermal expansion ceramics while continuously increasing attack angle, spindle speed and tool offset across rectangular regions. Material removal rate (MRR) and surface roughness (Ra) with respect to different process conditions are compared. With sufficient data, the processing ability using above three compliant machining technologies is summarized based on the MRR-Ra plots for different ceramics. In addition, microscopic observation and X-ray diffraction analysis are conducted to characterize differences in material behavior.

Adjustable Thermal Expansion Properties in Zr2MoP2O12/ZrO2 Ceramic Composites.

Zr2MoP2O12/ZrO2 composites were successfully synthesized by the solid state method in attempt to fabricate the near-zero thermal expansion ceramics. The phase composition, micromorphology and thermal expansion behavior of the Zr2MoP2O12/ZrO2 composites with different mass ratios were investigated using X-ray diffraction, scanning electron microscopy and thermal mechanical analysis. Results indicate that Zr2MoP2O12/ZrO2 composites can be prepared by pre-sintering at 500°C for 3 h and then sintering at 1050°C for 6 h. The resulting Zr2MoP2O12/ZrO2 composites consisted of orthorhombic Zr2MoP2O12 and monoclinic ZrO2. With increasing content of Zr2MoP2O12, the Zr2MoP2O12/ZrO2 ceramics became more compact and the coefficient of thermal expansion decreased gradually. Zr2MoP2O12/ZrO2 composites show an adjustable coefficient of thermal expansion (CTE) from 5.57 × 10−6 K−1 to −5.73 × 10−6 K−1 by changing the mass ratio of Zr2MoP2O12 and ZrO2. The Zr2MoP2O12/ZrO2 composite with a mass ratio of 2:1 showed near zero thermal expansion, and the average linear thermal expansion coefficient is measured to be 0.0065 × 10−6 K−1 in the temperature range from 25 to 700°C.

Thermal Expansion of SrZr<sub>4-x</sub>Ti<sub>x</sub>(PO<sub>4</sub>)<sub>6</sub> Ceramics

Low thermal expansion ceramics have been widely applied in multiple fields. In this paper, a series of low thermal expansion ceramics SrZr4-xTix(PO4)6 was prepared and characterized. The SrZr4-xTix(PO4)6 ceramics could be well sintered in the temperature range of 1400~1500 °C. The effect of the addition of Ti substituting Zr and the sintering temperature was studied. The Ceramic with x =0.1 sintered at 1450 °C, the SrZr4-xTix(PO4)6 had a high relative density. The thermal expansion coefficients were about 3.301×10-6 °C-1. It was demonstrated that the microstructure of the SrZr4-xTix(PO4)6 could be altered by adding varying amount of Ti to tailor the thermophysical properties of the material.

Preparation and Properties of NZP Family Ceramics

The matrix of NZP family ceramics is natrium phosphate zirconium (for short, NZP) . NZP family ceramics have the designabolity of thermal expansion coefficient, and the average thermal expansion coefficient can be changed from negative value to positive value by means of composition adjustment, thus obtaining zero thermal expansion ceramics with good thermal shock resistance. With NZP family ceramics the thermal stress can be effectively reduced and the thermal properties of materials can be enhanced.Therefore, NZP family ceramics have become a hot topic in materials science community in recent years.The calcium phosphate zirconium powder was prepared by coprecipitation method, and NZP family ceramics were prepared after pressing molding and pressureless sintering. The results show that the compressive strength of the prepared NZP family ceramics is 199 MPa and the thermal expansion coefficient is-0.5×10-6/°C at sintering temperature of 1100°C.

Synthesis, microstructure and thermal expansion studies on Ca0·5+x/2Sr0·5+x/2Zr4P6−2x Si2x O24 system prepared by co-precipitation method

We report on the synthesis, microstructure and thermal expansion studies on Ca0·5 + x/2Sr0·5 + x/2Zr4P6 − 2x Si2x O24 (x = 0·00 to 1·00) system which belongs to NZP family of low thermal expansion ceramics. The ceramics synthesized by co-precipitation method at lower calcination and the sintering temperatures were in pure NZP phase up to x = 0·37. For x ≥ 0·5, in addition to NZP phase, ZrSiO4 and Ca2P2O7 form as secondary phases after sintering. The bulk thermal expansion behaviour of the members of this system was studied from 30 to 850 °C. The thermal expansion coefficient increases from a negative value to a positive value with the silicon substitution in place of phosphorous and a near zero thermal expansion was observed at x = 0·75. The amount of hysteresis between heating and cooling curves increases progressively from x = 0·00 to 0·37 and then decreases for x > 0·37. The results were analysed on the basis of formation of the silicon based glassy phase and increase in thermal expansion anisotropy with silicon substitution.

Comparision of the Preparation Methods of Mesoporous Phosphate Compounds Belonging to NZP Family

Using polyethylene oxide (PEO) as template, the new types of mesoporous phosphate compound which belongs to NaZr2(PO4)3(NZP) family were synthesized by copreciptate, sol-gel and mechanochemical activation(MA) route respectively. The physical phase and pore structure of the synthesized powder materials were characterized by X-ray diffraction (XRD) and N2 adsorption–desorption. The results showed that the crystalline NZP family compound with mesoporous structure is formed by sol-gel route followed with calcination as well as MA method followed with hydrothermal treatment when the mole ratio of PEO to Zr is 1:10, and the specific surface area, average pore diameter and pore volume of the synthesized powder is 20-50m2/g, 3-6.nm and 0.05-0.12cm3/g respectively. The above research results indicate that it is promising to expand the application field of the powder of NZP family from low thermal expansion ceramics to catalytic materials.

Effect of MgO and PVA on the Synthesis and Properties of Negative Thermal Expansion Ceramics of Zr2(WO4)(PO4)2

A green synthesis of Zr2(WO4)(PO4)2 ceramics from ZrO2, WO3 and P2O5 is presented. It is shown that the ceramics can be synthesized by one‐step sintering within 60 min. The relative density of the ceramics can be enhanced from about 75% without sintering additives to 99.8% of the theoretical value with 1.0 wt% MgO and 2.0 wt% polyvinyl alcohol. The grain sizes of the ceramics are smaller and more uniform with MgO added in the raw materials than with MgO added in the Zr2(WO4)(PO4)2 powder. The coefficients of thermal expansion are about −2.325 × 10−6, −1.406 × 10−6, −1.509 × 10−6 and −1.384 × 10−6°C−1 for the samples without MgO, with MgO added in the raw materials, with MgO added in the Zr2(WO4)(PO4)2 powder and with MgO and PVA added in the raw materials, respectively.

Solid state sintering of very low and negative thermal expansion ceramics by Spark Plasma Sintering

Lithium aluminosilicate powder precursors of compositions Li2O:Al2O3:SiO2 as 1:1:2; and 1:1:3.11 were synthesized and sintered by the Spark Plasma Sintering technique. The sintering conditions were adjusted to obtain dense ceramic materials in an attempt to avoid the presence of a glassy phase. XRD and SEM images were employed for composition and microstructure characterization. The coefficient of thermal expansion of the sintered samples was studied down to cryogenic conditions. Rietveld quantification was performed with the use of an external standard. Pure β-eucryptite of different compositions in dense ceramic bodies was obtained with a negative expansion coefficient.

Negative Thermal Expansion Materials and Their Applications: A Survey of Recent Patents

Most materials expand on heating and contract on cooling. However, an increasing number of materials with negative thermal expansion (NTE) have been discovered in recent years. In this article, we review the patents related to the synthesis and applications of several important families of negative thermal expansion materials. Particular attention has been paid to the families of NTE materials with open framework structures consisting of corner-sharing polyhedra that are relatively rigid but flexible in rotation such as A(MO4)2 (A=Zr, Hf or combinations of them; M=W, Mo or combinations of them), A4+P2O7 (A is an element with valance of +4, A and P can also be partially replaced by other elements with charge balance), A2(MO4)3 (A=Sc, Y, Al, Lu etc. and may be partially substituted by other elements) and Zr2P2WO12, Ca1-xMxZr4P6O24 (M= Sr, Ba, Mg). Some patents with the family of NTE materials with a framework structure consisting of relatively soft polyhedra connected by stiff cyanide bridges such as Zn(CN)2 and Cd(CN)2, etc. and the family of the NTE materials of perovskite manganese nitrides whose NTE is driven by magnetovolume effect are also involved. The most important applications of the NTE materials are to compensate for undesired positive expansion of other materials, creating ceramics, composites or devices with controllable overall negative, zero or positive coefficient of thermal expansion. The patents related to these applications are reviewed. Some problems existing with particular materials or applications are commented. Keywords: Negative thermal expansion materials, negative thermal expansion ceramics, composites, low thermal expansion materials, zirconium tungstate, zirconnium molybdate, pyrophosphates, pyrovanadates, rare earth tungstate, rare earth molybdate, zirconium phosphate tungstate, sodium zirconium phosphate, zinc dicyanide, cadmium dicyanide, alkaline earth zirconium phosphates, perovskite manganese nitride

Synthesis and Characterization of Ca1-xSrxZr4(PO4) (0≤x

Different low thermal expansion ceramics of Ca1-xSrxZr4(PO4)6 system with x = 0, 0.25, 0.5 and 0.75 were synthesized by the solid state reaction method. After several heat treatments finished products were obtained at 1300°C. These were characterized for phase purity by X-ray Diffractometry and IR Spectroscopy. Densification parameters of the compositions with 3 and 5 wt% ZnO added as sintering aids were studied at 1100°, 1200° and 1300°C under soaking periods of 2-6 h. The corresponding effects on the physical, thermal and mechanical properties were observed. A maximum of 98% of theoretical density was obtained and flexural strength as high as 70 MPa was achieved. Thermal expansion varied from -0.47 to 2.65 x 10−6/°Cwith increase in Sr content. The results are discussed in the light of the microstructures.

Synthesis of low thermal expansion ceramics based on CaZr 4(PO 4) 6–Li 2O system

Ultra-low thermal expansion ceramics based upon CaZr 4(PO 4) 6–Li 2O system were synthesized through solid state sintering. Lithium oxide was introduced to the CaZr 4(PO 4) 6 lattice to promote liquid phase sintering to form CaZr 4(PO 4) 6 with strongly negative thermal expansion. A small addition of Li 2O has improved the densification rate, but also caused an excessive grain growth, which resulted in extensive microcracking. The microcracking lowered the bulk thermal expansion to −6×10 −6°C −1. Excessive amount of Li 2O content also led to formation of the secondary phase, Li 2Zr(PO 4) 2, and also caused the swelling of the CaZr 4(PO 4) 6 phase to lower the sintered density. An addition of over 5% of lithium oxide, the glass phase surrounding the CaZr 4(PO 4) 6 grain, together with the secondary phase increased the thermal expansion. At 2.5% addition, there was an indication that the viscous glassy phase has partially relieved the stresses associated with the thermal expansion anisotropy during cooling from the processing temperature. It was demonstrated that the microstructure of the CaZr 4(PO 4) 6 could be altered by adding varying amount of lithium oxide to tailor the thermophysical properties of the material.

NZP: A New Family of Low Thermal Expansion Ceramics

The NZP family, which gets its name after the prototype composition NaZr2P3O12, has received much attention in recent times because of their very low coefficient of thermal expansion (CTE), controlled lattice thermal expansion anisotropy, fast ionic conductivity, high thermal and chemical stability and flexibility towards ionic substitutions. Such materials can find widespread applications as exhaust components in automobiles, mirror blank for optical telescope, substrate materials for electronic packaging, as well as in sulphur batteries, nuclear waste immobilization, port-liners for diesel engines, braze fixtures for aircraft engines etc. The low expansion behaviour of NZP materials has been attributed to: (i) strongly bonded 3—dimensional network structure, (ii) existence of structural holes which may absorb some of the thermal vibrations and (iii) anisotropy in the thermal expansion of the lattice. In this overview the crystal structure, synthesis, thermal expansion behaviour and possible applications...

Anomalies in the thermal expansion of ceramic, injection moulded bodies

L'etude montre que des mesures de dilatation thermique sur une suspension ceramique de moulage par injection doivent etre precedees de traitements de recuit. L'utilisation d'un dilatometre permet d'enregistrer les effets des contraintes residuelles, malgre la decoupe d'echantillons de petites dimensions. Il ne s'agit pas actuellement d'une methode quantitative de mesure des contraintes residuelles

Thermal expansion of ceramics containing aluminum titanate

The investigation of the thermal expansion hysteresis facilitates, by relatively simple and available means, the obtaining of information about the presence in the ceramic material of active microcracks, that is, those capable of reverse collapse, and about their behavior during thermal cycling of the specimen. The presence of the expansion hysteresis in ceramics containing aluminum titanate exerts a considerable influence on their thermal behavior in working conditions. During thermal cycling of such ceramics in a relatively narrow temperature range (for example, from 700 to 900°C) no changes occur in the microcracked structure, and in this case the ceramic operates in the region of elastic deformations. However, with the expansion of the thermal cycling range brittle failure occurs in the intergrain bonds established at the higher temperature, which leads to the formation, after each cycle of heating and cooling, of a new system of microcracks, which reduce the strength of the bonds between the grains of the ceramic, and in the final account break it up.

Thermal expansion of ceramics in [formula omitted] - based solid solution systems

No systematic study on the thermal expansion behavior of Pb(Zn 1 3 Nb 2 3 ) O 3 - based ceramics has been made so far. This study is very important because these materials are potential candidates for multilayer capacitors and optical-mirrors substrates.Lead-zinc-niobate Pb(Zn 1 3 Nb 2 3 ) O 3 (PZN) based ceramics with perovskite structure are difficult to synthesize because of the formation of a undesirable pyrochlore phase. However, an addition of BaTiO 3, PbTiO 3 or SrTiO 3 stabilizes perovskite structure in PZN. In this work ceramic samples in the solid solution systems of PZN with these additives were prepared and thermal expansion measurements were carried out on the ceramic specimens using a push rod dilatometer. No substantial and systematic change in bulk thermal expansion with the change in composition was observed. Most of the samples demonstrated very low thermal expansion at lower temperature.