Top PDF Low temperature joining of ceramic composites

Low temperature joining of ceramic composites

Low temperature joining of ceramic composites

A method of joining similar or dissimilar ceramic and ceramic composite materials, such as SiC continuous fiber ceramic composites, at relatively low joining temperatures uses a solventless, three component bonding agent effective to promote mechanical bond toughness and elevated temperature strength to operating temperatures of approximately 1200 degrees C. The bonding agent comprises a preceramic precursor, an aluminum bearing powder, such as aluminum alloy powder, and mixtures of aluminum metal or alloy powders with another powder, and and boron powder in selected proportions. The bonding agent is disposed as an interlayer between similar or dissimilar ceramic or cermaic composite materials to be joined and is heated in ambient air or inert atmosphere to a temperature not exceeding about 1200 degrees C. to form a strong and tough bond joint between the materials. The bond joint produced is characterized by a composite joint microstructure having relatively soft, compliant aluminum bearing particulate regions dispersed in a ceramic matrix.
Show more

15 Read more

Low temperature joining of ceramic composites

Low temperature joining of ceramic composites

A method of joining similar or dissimilar ceramic and ceramic composite materials, such as SiC continuous fiber ceramic composites, at relatively low joining temperatures uses a solventless, three component bonding agent effective to promote mechanical bond toughness and elevated temperature strength to operating temperatures of approximately 1200 degrees C. The bonding agent comprises a preceramic precursor, an aluminum bearing powder, such as aluminum alloy powder, and mixtures of aluminum metal or alloy powders with another powder, and and boron powder in selected proportions. The bonding agent is disposed as an interlayer between similar or dissimilar ceramic or ceramic composite materials to be joined and is heated in ambient air or inert atmosphere to a temperature not exceeding about 1200 degrees C. to form a strong and tough bond joint between the materials. The bond joint produced is characterized by a composite joint microstructure having relatively soft, compliant aluminum bearing particulate regions dispersed in a ceramic matrix.
Show more

15 Read more

Fabrication of Glass Ceramic Fibres for High Temperature Applications

Fabrication of Glass Ceramic Fibres for High Temperature Applications

Figure 5.35 shows that tan δ curves follow a similar pattern. Tan δ is a damping coefficient that can be related to the impact resistance of a material [128]. Since the damping peak occurs in the region of the glass transition where the material changes from a rigid to a more mobile state, it is associated with the movement of small groups and chains of molecules within the polymer structure, all of which are initially frozen in. The higher the peak tan δ value, the greater the degree of molecular mobility. As expected, the peak tan δ values were higher for pure matrix material (1.31) than that for other composite. The tan δ peak of MAS glass ceramic composite (0.32) was lower and shifted by approximately 10°C from that of matrix material (I). Denser composites possessed peaks at lower temperatures, indicating that although the fibres were not misaligned, they were not perfectly bonded to the matrix. In addition to the low modulus value, (red arrow as shown in Figure 5.34) these composites were therefore observed to be less crosslinked with weaker interfaces, which agreed with the study by Kuzak and Shanmugam [129]. It can be seen that MAS glass composites (0.37) and LAS glass composites (0.40) provided a separation area between the matrix and fibre as shown Section 5.6.4. LAS glass composites showed the highest T g followed by LAS glass
Show more

192 Read more

Dielectric behavior of ceramic–graphene composites around the percolation threshold

Dielectric behavior of ceramic–graphene composites around the percolation threshold

phases are noticeable in the diffractogram corresponding to the composite with the largest amount of graphene. In this case, this is a very relevant result because some impurities, such as TiC, or different barium oxides could be expected in dense compacts if they were sintered by conventional methods. The use of SPS has allowed obtaining dense composites (theoretical density was around 100 % in all samples) by sintering them at low temperatures and for very short times. In order to study the structure of the graphene after sintering, Raman spectra were taken and are shown in Fig. 5b. Bands D (1355 cm −1 ) and G (1583 cm −1 ) are narrow and present similar intensities, with band D being even more intense than band G (ID/IG = 1.06). A qualitative comparison with the results by Botas et al. [22], considering the shapes and relative intensities of the D, G, and 2D bands, indicates that the state of the graphene in these compos- ites is very similar to graphene treated at 1000 °C in the reference given above, which agrees with the sintering temperature of 1100 °C. The 2D peak is centered around 2690 cm −1 and presents a single component; therefore, according to Ferrari et al. [23], the predominant number of stacked layers is one. These results demonstrate that graphite has not been formed.
Show more

7 Read more

HEAT TREATMENT OF CERAMIC   REINFORCED ALUMINUM MATRIX COMPOSITES-A REVIEW

HEAT TREATMENT OF CERAMIC REINFORCED ALUMINUM MATRIX COMPOSITES-A REVIEW

In recent years the use of Ceramic Reinforced Aluminum matrix composite material has increased very rapidly due to their high weight to strength ratio, low density, low thermal expansion coefficient, low maintenance and high temperature resistance. Metal Matrix Composites are widely used in aerospace and automotive engine components. The aluminum alloys are reinforced with ceramics like Alumina, Boron Carbide and Titanium Carbideetc and fabricated by stir casting,spray deposition, powder metallurgyprocedures etc. Heat treatment significantly affects the microstructure and enhances mechanical properties of these composites.In this paper the various research studies on heat treatment of aluminum matrix composites is reviewed with major focus on the heat treatment procedures, parameters ,microstructure and mechanical properties. The scope for further research in this area is also discussed. Keywords:Aluminum Matrix Composites,Heat Treatment, T4, T6, Solution heat treatment,Quenching, Age hardening, Microstructure, MechanicalProperties.
Show more

13 Read more

An Overview of Machining Process of Alumina and Alumina Ceramic Composites

An Overview of Machining Process of Alumina and Alumina Ceramic Composites

Advanced ceramic material have superior properties such as high hardness and strength at elevated temperatures, chemical inertness, high wear resistance, low thermal conductivity, high strength to weight ratio, high corrosion resistance, oxidation resistance, lower thermal expansion coefficient, low density, high-temperature stability, light weight, high compressive strength, a stronger electromagnetic response than that of metals and good creep resistance due to this it is used as wide application.

7 Read more

Fabrication and Characterization of Piezoelectric Ceramic Fiber/Aluminum Alloy Composites

Fabrication and Characterization of Piezoelectric Ceramic Fiber/Aluminum Alloy Composites

873 K is omitted because it is the same as Fig. 5 (b) ). From this, it can be seen that at T = 853 K, the amount of residual eutectic alloy is large. This may be attributed to the low temperature, which caused insufficient softening of the matrix material, resulting in less plastic deformation and more residual eutectic alloy. It can be seen that at T = 893 K, the amount of residual eutectic alloy is insignificant, but the piezoelectric fiber was damaged. As the temperature is high, softening of the matrix material might have proceeded, resulting in an increase in plastic deformation, which may have caused excess pressure on the piezoelectric fiber, leading to its rupture. In case of T = 873 K, the amount of residual eutectic alloy is less and damage to the piezoelectric fiber could not be seen, therefore, T = 873 K seems to be optimum temperature.
Show more

5 Read more

Comprehensive Ablation Characteristics of Ceramic Fibers Impregnated Rubber Composites

Comprehensive Ablation Characteristics of Ceramic Fibers Impregnated Rubber Composites

An ablative composite is a type of composites, which are used to protect certain structure or equipment from the intense heat environment. Mostly, such types of composites are used in aerospace industry. The basic definition of ablative composites is “These are highly endothermic sacrificial materials used to protect the hardware from ultra high temperatures and shear stresses in the propulsion system.” Low backface temperature, high mechanical/thermal ablation resistance, and good interfacial adhesion between the ablative material and the aerodynamic surface are required for the composites used in Thermal Protection Systems (TPS)[3]. The main function of TPS materials is to protect the inner hardware of space vehicles and ballistic missiles from ultrahigh temperature/velocity flow of gases encountered during their missions. Crosslinked polymer composites have been used as TPS materials since long time due to their excellent thermal resistance, ablation resistance, low backface temperature evolution during ablation, and low density characteristics. Phenolic resin based polymer composites have high backface temperature elevation and low interfacial bonding with the metallic casings but high erosion resistance compared to the elastomeric crosslinked composites, i.e., ethylene propylene diene monomer rubber (EPDM), silicon rubber (SR), and acrylonitrile butadiene rubber (NBR) based composites. Silica/silicon carbide fibers impregnated polymer composites, carbon–carbon composites, phenolic composites and elastomeric composite tiles have been used to protect reentry vehicles and solid rocket motor from ultrahigh temperature environments[4]-[5].
Show more

6 Read more

Thermal analysis of joining thermoplastic matrix composites using microwaves

Thermal analysis of joining thermoplastic matrix composites using microwaves

Abstract: Industrial microwave technology for processing polymers and polymer-based composites is currently in a state of considerable flux. Ku et al. (1997a; 1997b; 1999a) used the equipment shown in Figure 1 to join random glass or carbon fibres reinforced thermoplastic composites. The material used for the research is 33% by weight random glass fibre reinforced low-density polyethylene [LDPE/GF (33%)] using Araldite as primer. The heat absorbed and heat flow in the sample materials are studied. The temperatures at different points of the samples are also measured using infrared thermometer. The effect of power input and cycle time on the temperature distribution in the test piece is detailed together with the underlying principles of sample material interactions with electromagnetic field.
Show more

27 Read more

Joining and interfacial properties of aluminum/glass fiber reinforced polypropylene sandwich composites

Joining and interfacial properties of aluminum/glass fiber reinforced polypropylene sandwich composites

polymer matrices. However, such thermosetting-based composites are often brittle and, for optimum consolidation of parts made from prepreg, elevated processing temperature and pressure are required for a prolonged period. Recent attention has focused on thermoplastic-based composites since they offer a number of advantages such as rapid manufacturing and recyclability. In comparison, metal-polymer laminates with thermoplastic-based composites offer improved toughness and has the potential for short process cycle times. This can lead to rapid, low-cost production of structural components. Here, the use of a thermoplastic-based composite ensures the production of aerospace and automotive panels and components that can be molded, bonded to a metal substrate and shaped in a simple oneshot manufacturing operation. This procedure clearly offers an attractive option for reducing both the cycle time and associated manufacturing costs. In addition, the high recyclability and low volatiles offered by thermoplastics are key factors for vehicle manufacturers; the low density and low cost of polypropylene is particularly attractive. Although PP is difficult to join, glass fiber- reinforced polypropylene is of particular interest due to its relatively low cost (Reyes and Kang 2007).
Show more

75 Read more

Selective Area Laser Deposition For The Purpose Of Ceramic Joining And Repair

Selective Area Laser Deposition For The Purpose Of Ceramic Joining And Repair

It is possible to use a compound that is a liquid at STP provided that this liquid can be vaporized and remain in the gas phase for the duration of the experiment. In order for this to be the case the compound must have a sufficient equilibrium vapor pressure at the temperature of the reaction chamber. While certain chemical vapor deposition reactions utilize low partial pressures of reactive gasses, (< 1 torr), these reactions produce very small volumes of deposited material making build times prohibitively long. SALD reactions require that much greater volumes of deposited material be produced in a localized area. Deposition volume is of the order of cubic mm. A higher vapor pressure allows increased reaction rates and greater volume of deposit per volume of reaction chamber. [24][32][40] For SALD reactions it is preferable to have precursors with equilibrium vapor pressures in the range of the tens to hundreds of torr. [32] A lower limit is not fixed but equilibrium vapor pressures >5 torr will greatly facilitate the growth of SALD deposits on the macro scale.
Show more

138 Read more

Thermal protection of carbon fiber-reinforced
composites by ceramic particles

Thermal protection of carbon fiber-reinforced composites by ceramic particles

The drive to reduce weight and hence fuel consumption has promoted the use of fiber-reinforced composites in the transport industry. Modern aircraft such as the Boeing 787 and Airbus 350 are increasingly using composites as primary structural components. However, when polymeric structures replace metallics, their thermal stability becomes an important issue. On exposure to heat, the resin part of the composite softens before degrading and then undergoes combustion, often accompanied by delamination, which affects the structural integrity of the composite structure. The thermal and fire performances of fiber-reinforced composites depend upon the resin and fiber type, their mass/volume fraction composition and fiber configuration [1,2]. When exposed to high heat fluxes, the heat transfer and the resulting temperature rise through the thicknesses of samples depend on the density, thermal conductivity, and specific heat capacity values of both the resin and fiber components, as well as the kinetics of their decomposition [3–5], although the latter is applicable to resins only in the case of these composites. The thermal and mechanical performance of most thermosetting resins is dictated by their functionality. Low-functional resin systems such as bi-functional diglycidyl ether of bisphenol A
Show more

14 Read more

Joining of Ceramics and Ceramic Matrix Composites (CMC) for Aerospace and Energy Applications

Joining of Ceramics and Ceramic Matrix Composites (CMC) for Aerospace and Energy Applications

Microwave processing is one of the emerging technology adopted in fabrication of ceramics, ceramic matrix composites, polymer and polymer matrix composites due to rapid source of heating [65]. The foremost benefit of using microwaves in joining is that it does not heat the complete assembly, but only the joint area or interfaces, as for laser joining previously discussed. The high temperature and detrimental pressure effect on the whole substrates can also be avoided. This is one of the fastest joining technique, in principle, large and complex pieces/parts can be joined at a low cost. Microwaves are capable to achieve a temperature 2000 o C with a frequency of 2.45 GHz and a power of 700 W [15, 17, 66]. Microwaves have been effectively employed for joining of ceramics (alumina, zirconia, SiC), ceramic matrix composites (SiC/SiC) [67-69] metals (Copper, stainless steel) [70, 71] and polymer matrix composites [72]. Different fillers such as glasses [73, 74], alumina gel [75], Al-Si-powders [76], TICUSIL paste [77, 78] and NiTi foils [79] were used in microwave assisted joining.
Show more

177 Read more

Synthesis, Characterization and Dielectric Study of Polypyrrole/Zinc Tungstate (Ceramic) Composites

Synthesis, Characterization and Dielectric Study of Polypyrrole/Zinc Tungstate (Ceramic) Composites

Copyright to IJIRSET www.ijirset.com 13941 The most important and reliable factor in the study of heat stable polymers is the measurement or evaluation of thermal stability. Thermal properties and interaction between the polymers can also be noted from the oxidative degradation curves through thermo-gravimetric analysis (TG/DTA) studies. DTA is most commonly used to determine transition temperatures such as glass transitions, melting cross-linking reactions and decomposition. However, it measures only the total heat flow and the sum of all thermal transitions in the sample.The representative TG/DTA curve for pure PPy is shown in Figures 4.a. The materials have been heated from 40 °C to 740 °C under a constant heating rate of 10 °C/min and in the inert atmosphere of nitrogen gas. Variation of weight is almost linear and the maximum polymer decomposition temperature is there from 40 °C to 740 °C for all. In the Figure 4.a, two major weight loss stages for PPy were observed at 110 °C to 130°Cand 736.3°C.
Show more

13 Read more

Preparation and characterization of novel antibacterial nano- ceramic-composites for bone grafting

Preparation and characterization of novel antibacterial nano- ceramic-composites for bone grafting

Novel nanocomposites scaffolds were prepared by impregnating nano-calcium phosphate (HA)/ walled carbon nanotube ( MWCNT)/ZnO nano-particles into the alginate polymers matrix. The nano-composite materials were characterized using X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR) analyses mechanical test and Scanning Electron Microscopy (SEM) before in- Vitro and antibacterial test. The in-vitro behavior was assessed via measurement of calcium and phosphorus ions in SBF (simulated body fluid). FT-IR and SEM of the composites were performed pre and post immersion in SBF. The results prove that the bone like apatite layer formation was enhanced on the biopolymeric composite surface more than that on the polymeric composite containing more MWCNT. Therefore, the data confirmed that MWCNT plays an important role in the enhancement of the apatite formation. The conclusions proved that the MWCNT /polymeric biocomposites, containing more of MWCNT, are promising for antibacterial and bone remodeling applications.
Show more

18 Read more

Analysis of multiple cracking in metal/ceramic composites with lamellar microstructure

Analysis of multiple cracking in metal/ceramic composites with lamellar microstructure

Wanner and Roy (2008) have studied metal-ceramic composites produced at Institute of Applied Materials-Ceramic Materials and Technologies at Karlsruhe Institute of Technology, Karlsruhe, Germany. These composites were produced from alumina preforms prepared by freeze-casting and subsequent sintering by infiltrating them with aluminium-silicon alloy using a squeeze-casting technique. The resulting metal/ceramic composites were found to possess hierarchical lamellar microstructure with randomly orientated individual regions (domains), in which all ceramic and metallic lamellae are parallel to each other. Domains had sizes of up to several millimeters while thicknesses of alternating ceramics and metallic lamellae were from 20 to 200 μm (Roy and Wanner 2008). Individual domains were found to exhibit a pronounced anisotropy, with the freezing direction being the stiffest and strongest. Failure in this direction occurred in a brittle manner, while other directions were controlled by the alloy and exhibited extensive ductility (Roy, Butz and Wanner, 2010). In the subsequent studies, complete set of anisotropic elastic properties of these composites was determined experimentally using ultrasound phase spectroscopy and resonant ultrasound spectroscopy and predicted using micromechanical modelling (Ziegler et al, 2010, Roy et al, 2011). A study of single-domain samples taken from these composites was also undertaken (Sinchuk et al, 2013) focusing on the compressive response and elasto-plastic behavior. Launey et el (2010) used freeze-casting or ‘ice templating’ to create fine scale laminated metal/ceramic bulk composites, with ceramic contents of 36% and with lamellae thickness down to 10 microns, fracture toughness of 40 MPa-m 0.5 and tensile strength of approximately 300 MPa.
Show more

33 Read more

The effect of low temperature air plasma treatment on physico-chemical properties of kaolinite/polyethylene composites

The effect of low temperature air plasma treatment on physico-chemical properties of kaolinite/polyethylene composites

crystallinity (Xc) calculated according to Jung et al. [29-31]. As given in Table 5, with increasing degree of filling of PE polymer macromolecular matrix a decrease of the fusion enthalpy was found to be accompanied with a decrease of the melting point temperature. This fact indicates successful disruption of the PE macromolecular oriented higher degree structure. When crystallized from dilute solution, PE polymers display the characteristic platelet or lamella structure. It has been well established, that the chain axes are preferentially normal to the wide faces of the lamella. Hence, a given polymer molecule must traverse a crystallite many times. Based on earlier electron microscopy observations, it has been presumed that this interface is comprised of regularly folded chains. However approximately 15-20% of the chain units must be in non-ordered conformations. This triggers the conclusion that the presence of such a large number of non-crystalline chain units leads to the presence of a disordered amorphous overlayer [30]. The above conclusions correspond well to our findings as with an increasing degree of filling the crystallinity decreased as well (see Table 5).
Show more

29 Read more

Towards understanding the cutting and fracture mechanism in ceramic matrix composites

Towards understanding the cutting and fracture mechanism in ceramic matrix composites

mode, it is observed that the material experiences an important change in the energy release rate according to the brittle-to-semi-ductile transi- tion occurring while reducing the depth of cut. Finally, a novel monitoring method based on the vibrations of the sample has been found successful to understand the type of crack formation appearing while cutting CMCs. Keywords: Machining, Ceramic Matrix Composites, Orthogonal cutting, Fracture mechanism, Crack formation

36 Read more

Impedance model for a high-temperature ceramic humidity sensor

Impedance model for a high-temperature ceramic humidity sensor

with deep donors 3 eV below the conduction band (Pan et al., 2013). Therefore, most donors are not ionized at 320 ◦ C, leading to a temperature dependence of the electronic con- ductance. This can be described by an ohmic resistor, which can be seen in the phase plots of Figs. 3 and 4, since the maximum phase angle of the sensor in dry air collapses at about − 0.1 ◦ , whereas all humid measurements show a com- mon maximum phase at around − 6.25 ◦ . This angle repre- sents a strongly resistive CPE, the ionic pathway, which does not exist at 0 mbar humidity.

9 Read more

Effect of Sintering Temperature on the Properties and Microstructure of A Ceramic Product

Effect of Sintering Temperature on the Properties and Microstructure of A Ceramic Product

Human activities are always connected with the uses of ceramic materials or ceramic product in every day life. Ceramic materials are typically produced by the application heat upon processed clay and other natural raw materials to form a rigid body. In the present investigation, the mixture of ball Clay, quartz and feldspar are made standard bodies sintered at 900-1050°C and the Ceramic bodies are studied some important properties like, Bulk density, Compressive strength, Porosity, Appearance, Colour and the microstructure analysis of Ceramic bodies using SEM technique.
Show more

5 Read more

Show all 10000 documents...