The influence of heat treatment on the fiber/matrix interface in a SiC-reinforced glassceramic

1988 ◽  
Vol 46 ◽  
pp. 742-743
Author(s):  
E. Bischoff ◽  
O. Sbaizero
Keyword(s):  
Heat Treatment ◽  
Aluminum Silicate ◽  
Lithium Aluminum ◽  
Interfacial Region ◽  
Specimen Preparation ◽  
Crack Wake ◽  
Pull Out ◽  
Annealed Material ◽  
Ultrasonic Drilling ◽  
Fiber Matrix Interface

Fiber or whisker reinforced ceramics show improved toughness and strength. Bridging by intact fibers in the crack wake and fiber pull-out after failure contribute to the additional toughness. These processes are strongly influenced by the sliding and debonding resistance of the interfacial region. The present study examines the interface in a laminated 0/90 composite consisting of SiC (Nicalon) fibers in a lithium-aluminum-silicate (LAS) glass-ceramic matrix. The material shows systematic changes in sliding resistance upon heat treatment.As-processed samples were annealed in air at 800 °C for 2, 4, 8, 16 and 100 h, and for comparison, in helium at 800 °C for 4 h. TEM specimen preparation of as processed and annealed material was performed with special care by cutting along directions having the fibers normal and parallel to the section plane, ultrasonic drilling, dimpling to 100 pm and final ionthinning. The specimen were lightly coated with Carbon and examined in an analytical TEM operated at 200 kV.

scholarly journals FEATURES OF THE STRUCTURE FORMATION OF SPODUMENS-CONTAINING GLASS-CRYSTAL MATERIALS AFTER HEAT TREATMENT

2021 ◽  
pp. 38-43
Author(s):  
Oksana Savvova ◽  
Gennady Voronov ◽  
Svіatoslav Rіabinin ◽  
Alexey Fesenko ◽  
Dmitry Svishov
Keyword(s):  
Heat Treatment ◽  
Low Temperature ◽  
Ir Spectra ◽  
Structure Formation ◽  
Glass Network ◽  
Temperature Treatment ◽  
Aluminum Silicate ◽  
Lithium Aluminum ◽  
Two Stage ◽  
Crystalline Materials

The promising areas of application of spodumene–containing glass–crystalline materials in various branches of science and technology, in particular, to increase the defense capability of the state, have been determined. The relevance of the development of lightweight high–strength sitalls based on them, taking into account the aspects of energy saving for obtaining armored elements, has been determined. It has been established that the use of IR spectroscopy is promising for studying the nanostructure of glass–crystalline materials. The compositions of lithium aluminum silicate glasses and the modes of their heat treatment have been developed. The features of the structure formation of spodumene–containing glass–crystalline materials obtained under the conditions of two–stage low–temperature heat treatment have been investigated. Taking into account the analysis of the nature of the IR spectra of chain silicates, the structure of glass–crystalline materials was investigated according to the IR spectra and the nature of structure formation was established depending on the initial composition of the glass. It has been established that the formation of a structural glass network with the participation of tetrahedra [AlO4], [BO4] and [SiO4] and the presence of cybotaxic groups [Si2O6] allows, under conditions of two–stage low–temperature treatment, to provide bulk crystallization of spodumene–containing glass–crystalline materials. It has been established that the formation of the vitrified structure of glass–crystalline materials allows to ensure their high values of Vickers hardness, microhardness and crack resistance and by the presence of a glass phase, which plays the role of a damper, to ensure their high armor resistance. This will increase the efficiency and make it possible to use them as an energy–destructive and energy–absorbing layer in the composition of the armor element «metal alloy – ceramics – sitall». The introduction of spodumene–containing glass–crystalline materials will increase the competitiveness of competitive domestic armored elements for personal protection.

Characterization of Boron Nitride Coated Silicon Carbide Fibers and Composites

1997 ◽  
Vol 3 (S2) ◽  
pp. 733-734
Author(s):  
Mani Gopal
Keyword(s):  
Silicon Carbide ◽  
Boron Nitride ◽  
High Temperatures ◽  
Specimen Preparation ◽  
Ion Milling ◽  
Sic Fibers ◽  
Silicon Carbide Fibers ◽  
Pull Out ◽  
Sic Composites

Silicon carbide (SiC) composites are receiving much attention for structural use at high temperatures. One class of composites are those reinforced with SiC fibers. The SiC fibers are coated with boron nitride (BN) which is weakly bonded to the fiber. During fracture, the coating deflects cracks causing pull-out of the fibers (Fig. 1). This process of fiber pull-out consumes energy and increases the toughness of the composite. Although much work has been done on characterizing these materials by SEM, not much has been done using TEM due to difficulties in specimen preparation. The purpose of this study is to characterize these fibers and composites using conventional and analytical TEM.In this study, TEM specimens were prepared by dimpling and ion milling. Careful control of the preparation was needed to ensure the integrity of the SiC-BN interface. Figure 2a is a TEM image of the fiber showing delamination at the SiC-BN interface.

scholarly journals Influence of Oxidation Damages on Mechanical Properties of SiC/SiC Composite Using Domestic Hi-Nicalon Type SiC Fibers

Scanning ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Enze Jin ◽  
Denghao Ma ◽  
Zeshuai Yuan ◽  
Wenting Sun ◽  
Hao Wang ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Tensile Modulus ◽  
Treatment Temperature ◽  
Matrix Interface ◽  
Oxidation Treatment ◽  
Pull Out ◽  
Special Surface ◽  
Higher Temperature ◽  
Fiber Matrix Interface ◽  
Fiber Matrix

Here, we show that when the oxidation treatment temperature exceeded 600°C, the tensile strength of SiC/SiC begins to decrease. Oxidation leads to the damages on the PyC fiber/matrix interface, which is replaced by SiO2 at higher temperature. The fracture mode converts from fiber pull-out to fiber-break as the fiber/matrix interface is filled with SiO2. Oxidation time also plays an important role in affecting the tensile strength of SiC/SiC. The tensile modulus decreases with temperature from RT to 800°C, then increases above 800°C due to the decomposition of remaining CSi x O y and crystallization of the SiC matrix. A special surface densification treatment performed in this study is confirmed to be an effective approach to reduce the oxidation damages and improve the tensile strength of SiC/SiC after oxidation.

Formation of NaNbO3 Crystals in Dielectric Glass and Glass-Ceramics of a Na2O-Nb2O5-Al2O3-SiO2 System

2008 ◽  
Vol 55-57 ◽  
pp. 229-232 ◽  
Author(s):  
S. Thongsaeng ◽  
Anuson Niyompan ◽  
Rungnapa Tipakontitikul ◽  
Kamonpan Pengpat
Keyword(s):  
Heat Treatment ◽  
Treatment Time ◽  
Glass Ceramics ◽  
Glass Production ◽  
Nucleating Agent ◽  
Aluminum Silicate ◽  
Phase Identification ◽  
Dielectric Glass ◽  
Xrd Patterns ◽  
Glass Compositions

Dielectric glass and glass-ceramics were derived from Na2O-Nb2O5-Al2O3-SiO2 system. Small amount of TiO2 were also introduced into glass compositions to study crystallization behavior of the glass with present of this nucleating agent. Conventional melt-quenching technique was employed for a glass production and the selected bulk glass samples were subjected to the heat-treatment process at appropriate temperature. After six different glass compositions were produced, and by observation with necked eyes, all obtained glass samples are in light brown color and some samples were opaque due to crystallization took place during quenching. Phase identification through XRD patterns show that there were 3 phases, NaNbO3, NaNbO8 and a sodium aluminum silicate compound, found in those opaque glass samples. NaNbO3 is a predominant phase in all samples. Fortunately, clear transparent glass was obtained from the composition with no TiO2 addition. Heat treatment of this glass did not induce phase change, three aforementioned phases still present. Increasing heat treatment time promoted a higher of observed intensity of NaNbO3. But the NaNbO3 crystalline size was not significantly developed with time. The dielectric response of the NaNbO3 crystals in the glass-ceramics samples are influenced by presence of other crystalline phases.

Interfacial Reactions in the Al/Si3N4/Si and Au/Si3N4/Si Systems

1989 ◽  
Vol 153 ◽  
Author(s):  
F. Edelman ◽  
E. Gutmanas ◽  
R. Brener
Keyword(s):  
Heat Treatment ◽  
Diffusion Barrier ◽  
Interfacial Reactions ◽  
Interfacial Region ◽  
Small Islands ◽  
Interface Chemistry

AbstractThe interface chemistry and structure of thin Al and Au films deposited on Si3N4 have been studied. In the case of Al/Si3N4 system, an interfacial AIN like layer was observed in the as-deposited state. The thickness of this layer was found to increase with increasing the temperature up to 600°C. This thin AlN layer acts as a diffusion barrier which prevents Al to diffuse into Si3N4 Furthermore, Si released in the reaction between Al and Si3N4 appears to crystallize into small islands dispersed in the interfacial region. In contrast to Al, no reaction between Au and Si3N4 was observed in the as-deposited state. However, after heat treatment at temperatures higher than 400°C gold silicides (Au5Si2,Au2Si,Au3Si) with a very thin Si layer accumulated on the Au surface were observed.

Dispersion and thermal properties of lithium aluminum silicate glasses doped with Cr^3+ ions

2006 ◽  
Vol 45 (30) ◽  
pp. 7818 ◽  
Author(s):  
Fouad El-Diasty ◽  
Manal Abdel-Baki ◽  
Fathy A. Abdel Wahab ◽  
Hussein Darwish
Keyword(s):  
Thermal Properties ◽  
Silicate Glasses ◽  
Aluminum Silicate ◽  
Lithium Aluminum
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