Microstructural and fractographic characterization of B4C-Al cermets tested under dynamic and static loading

1989 ◽  
Vol 47 ◽  
pp. 562-563
Author(s):  
Gyeung Ho Kim ◽  
Mehmet Sarikaya ◽  
D. L. Milius ◽  
I. A. Aksay
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Static Loading ◽  
Carbon Deposition ◽  
Full Density ◽  
Unique Combination ◽  
Strong Component ◽  
Reaction Products

Cermets are designed to optimize the mechanical properties of ceramics (hard and strong component) and metals (ductile and tough component) into one system. However, the processing of such systems is a problem in obtaining fully dense composite without deleterious reaction products. In the lightweight (2.65 g/cc) B4C-Al cermet, many of the processing problems have been circumvented. It is now possible to process fully dense B4C-Al cermet with tailored microstructures and achieve unique combination of mechanical properties (fracture strength of over 600 MPa and fracture toughness of 12 MPa-m1/2). In this paper, microstructure and fractography of B4C-Al cermets, tested under dynamic and static loading conditions, are described.The cermet is prepared by infiltration of Al at 1150°C into partially sintered B4C compact under vacuum to full density. Fracture surface replicas were prepared by using cellulose acetate and thin-film carbon deposition. Samples were observed with a Philips 3000 at 100 kV.

Mechanical Characterization of Dense Hydroxyapatite Blocks

2006 ◽  
Vol 514-516 ◽  
pp. 1083-1086
Author(s):  
Cláudia M.S. Ranito ◽  
Fernando A. Costa Oliveira ◽  
João P. Borges
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Physical And Mechanical Properties ◽  
Full Density ◽  
Indentation Fracture ◽  
Mechanical Characterisation ◽  
Indentation Fracture Toughness ◽  
Ft Ir

Bioactive dense HAp ceramics possess a unique set of properties, which make them suitable as bone substitute. However, both physical and mechanical properties of HAp have to be evaluated in order to produce new materials that match the bone stiffness. This paper highlights the influence of both porosity and grain size on the four-point flexural strength and the indentation fracture toughness of pure dense HAp blocks sintered at 1300°C. Both discs and rectangular bars were produced by uniaxial pressing at 40MPa and sintered in static air at temperatures between 1150 and 1325°C for 1 h in order to assess the densification behaviour of the P120S medical grade HAp powder used. After sintering, both the density and the open porosity were measured. In addition to FT-IR, XRD and SEM, the mechanical properties of the dense HAp blocks, including Young´s modulus, flexural strength, Vicker´s hardness and fracture toughness, were characterized and whenever possible these properties were compared to those reported for cortical bone. Pressureless sintering to full density at temperatures below 1300°C does not occur for the stoichiometric powder used. The results obtained underline the importance of full mechanical characterisation of dense HAp so that new implant materials can be developed. There is a need to improve the microstructure and thus enhance mechanical strength of HAp ceramics, as it was found that flexural strength is closely related to the micropores present in the sintered samples.

Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

1989 ◽  
Vol 47 ◽  
pp. 556-557
Author(s):  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Frictional Stress ◽  
Fiber Reinforced ◽  
Pull Out ◽  
Carbon Coated ◽  
Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

Preparation and Characterization of Alumina based TiNn and SiCn Composites

2002 ◽  
Vol 740 ◽  
Author(s):  
Mats Carlsson ◽  
Mats Johnsson ◽  
Annika Pohl
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Growth ◽  
Ceramic Composites ◽  
Processing Route ◽  
Nano Structure ◽  
Plasma Sintering ◽  
Water Based ◽  
Spark Plasma

ABSTRACTCeramic composites containing 2 and 5vol. % of nanosized commercially available TiN and SiC particles in alumina were prepared via a water based slurry processing route followed by spark plasma sintering (SPS) at 75 MPa in the temperature range 1200–1600°C. Some of the samples could be fully densified by use of SPS already after five minutes at 1200°C and 75 MPa. The aim was to control the alumina grain growth and thus obtain different nano-structure types. The microstructures have been correlated to some mechanical properties; e.g. hardness and fracture toughness.

Microstructure and Mechanical Properties of Spark-Plasma-Sintered SiC-TiC Composites

2005 ◽  
Vol 287 ◽  
pp. 335-339 ◽  
Author(s):  
Kyeong Sik Cho ◽  
Kwang Soon Lee
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Heating Rate ◽  
Spark Plasma Sintering ◽  
Sintering Temperature ◽  
Applied Pressure ◽  
Argon Atmosphere ◽  
Full Density ◽  
Plasma Sintering ◽  
Spark Plasma

Rapid densification of the SiC-10, 20, 30, 40wt% TiC powder with Al, B and C additives was carried out by spark plasma sintering (SPS). In the present SPS process, the heating rate and applied pressure were kept at 100°C/min and at 40 MPa, while the sintering temperature varied from 1600-1800°C in an argon atmosphere. The full density of SiC-TiC composites was achieved at a temperature above 1800°C by spark plasma sintering. The 3C phase of SiC in the composites was transformed to 6H and 4H by increasing the process temperature and the TiC content. By tailoring the microstructure of the spark-plasma-sintered SiC-TiC composites, their toughness could be maintained without a notable reduction in strength. The strength of 720 MPa and the fracture toughness of 6.3 MPa·m1/2 were obtained in the SiC-40wt% TiC composite prepared at 1800°C for 20 min.

Fabrication and Characterization of Alumina/Zirconia Ceramic Compound

2012 ◽  
Vol 724 ◽  
pp. 249-254 ◽  
Author(s):  
Bum Rae Cho ◽  
Ji Hoon Chae ◽  
Bo Lang Kim ◽  
Jong Bong Kang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Low Temperature ◽  
Mechanical Strength ◽  
Sem Analysis ◽  
Zirconia Ceramic ◽  
Sintering Process ◽  
Sintering Aids ◽  
X Ray Diffraction

Sintered ZTA(zirconia toughened alumina) which has good mechanical properties at a low temperature was produced by milling and mixing with Al2O3 and ZrO2(3Y-TZP). In order to examine the effect of sintering aids on the mechanical properties of ZTA, fracture toughness and hardness of the produced ZTA were observed in accordance with change of the added quantity of ZrO2 Scanning electron microscopy and X-ray diffraction technique were applied to observe microstructural change and phase transformation during the process. Experimental results showed that the addition of sintering aids in ZTA at a low temperature induced densification and adding SiO2 and talc lowered sintering temperature and promoted crystallization process of the compound. The mechanical strength of ZTA added ZrO2 showed higher mechanical strength and SEM analysis revealed that Al2O3 and ZrO2 during the sintering process restrained the grain growth each other. Especially, the 92% Al2O3 added sintering aids showed more than 98% of the theoretical density and more than 1500 Hv of hardness value at a low temperature of 1400. It was also showed that the fracture toughness is gradually increasing first and decreasing later in accordance with the quantity of ZrO2.

Composites for the 1990s

1987 ◽  
Vol 322 (1567) ◽  
pp. 409-423 ◽  
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Polymer Composites ◽  
Laminated Composite ◽  
Crack Arrest ◽  
Unique Combination ◽  
Different Types

Composites are of two essentially different types: ( a ) those made to achieve a unique combination of properties, usually mechanical properties; ( b ) composites formed for ease of processing. The archetype of ( a ) is the fibre or laminated composite. The attainable properties will be reviewed and interesting effects arising from the scale of size of the components discussed, notably crack arrest and thin-film effects. Examples of ( b ) are polymer-polymer composites and some of the processes for forming ceramics and strong metals. A unified example of ( a ) and ( b ) are composites of controlled thermal conductivity.

scholarly journals Microstructure and Materials Properties of Understoichiometric TiBx Thin Films Grown by HiPIMS

2020 ◽  
Author(s):  
Jimmy Thörnberg ◽  
Justinas Palisaitis ◽  
Niklas Hellgren ◽  
Fedor Klimashin ◽  
Naureen Ghafoor ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Fracture Toughness ◽  
Planar Defects ◽  
Materials Properties ◽  
Apparent Fracture Toughness ◽  
Research Article ◽  
Tissue Phase

<p>In the present research article we report synthesis of TiB<sub>x</sub>, 1.43<i>n-situ</i> mass- and energy-spectroscopy is used to explain the obtained compositional range. Excess B in overstoichiometric TiB<i><sub>x</sub></i><sub> </sub>thin films from DCMS results in a hardness up to 37.7±0.8 GPa, attributed to the formation of an amorphous B-rich tissue phase separating stoichiometric TiB<sub>2</sub> columnar structures. With a particular focus on characterization of the understoichiometric samples, we show that understoichiometric TiB<sub>1.43</sub> thin films synthesized by HiPIMS exhibit a superior hardness of 43.9±0.9 GPa, where the deficiency of B is found to be accommodated by Ti planar defects. The apparent fracture toughness, electrical resistivity and thermal conductivity of the same sample is 4.2±0.1 MPa√m, 367±7 μΩ·cm and 5.1 W/(m.K), respectively, as compared to corresponding values for overstoichiometric TiB<sub>2.20</sub> DCMS thin film samples of 3.2±0.1 MPa√m, 309±4 μΩ·cm and 3.0 W/(m.K). </p>

Processing and characterization of B4C-Al laminated cermets

1990 ◽  
Vol 48 (4) ◽  
pp. 1022-1023
Author(s):  
Mehrdad Yasrebi ◽  
Gyeung H. Kim ◽  
David L. Milius ◽  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Fracture Strength ◽  
Laminated Composites ◽  
Laminated Composite ◽  
Type A ◽  
Type B ◽  
Body Type ◽  
Metal Infiltration

B4C-Al composites show enhanced fracture strength and fracture toughness values over monolithic B4C.1-2 A controlled change in structural morphologies such as lamination further enhances mechanical properties of the composite over the B4C-Al composites processed to form a monolithic morphology. This paper summarizes microstructure-property correlations studied in B4C-Al laminated composites.The laminated composite is formed either by metal infiltration of B4C tapes sandwiched with Al sheets, type (a), (Fig. 1a) or by lamination of B4C tapes of different porosity and then subjected to metal infiltration of the laminated body, type (b), (Fig. 1b). In the first method, after thin tapes of B4C were formed, each tape was individually sintered between polished graphite discs, then layered with Al sheets, and the entire stack was heated to induce infiltration. In the second method, tapes of B4C with different green densities were stacked and laminated under pressure and temperature. The laminated body was then sintered and subsequently infiltrated with Al.

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