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- Bartek, Alena, et al.
(författare)
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Yttrium α-Sialon Ceramics by Hot Isostatic Pressing and Post-Hot Isostatic Pressing
- 1992
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Ingår i: Journal of The American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 75:2, s. 432-439
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Tidskriftsartikel (refereegranskat)abstract
- Dense α-sialon materials were produced by hot isostatic pressing (HIP) and post-hot isostatic pressing (post-HIP) using compositions with the formula Yx(Si12-4.5x, Al4.5x)-(O1.5x,N16-1.5x) with 0.1 ≤x ≤ 0.9 and with the same compositions with extra additions of yttria and aluminum nitride. X-ray diffraction analyses show how the phase content changes from large amounts of β-sialon (x = 0.1) to large amounts of α-sialon (x = 0.4) and increasing amounts of mellilite and sialon polytypoids (x = 0.8). Samples HIPed at 1600°C for 2 h contained unreacted α-silicon nitride, while those HIPed at 1750°C for 1 h did not. This could be due to the fact that the time is to short to achieve equilibrium or that the high pressure (200 MPa) prohibits α-sialon formation. Sintering at atmospheric pressure leads to open porosity for all compositions except those with excess yttria. Therefore, only samples with excess yttria were post-HIPed. Microstructrual analyses showed that the post-HIPed samples had the highest α-sialon content. A higher amount of α-sialon and subsequently a lower amount of intergranular phase were detected at x = 0.3 and x = 0.4 in the post-HIPed samples in comparison to the HIPed. The hardness (HV10) and fracture toughness (KIC) did not differ significantly between HIPed and post-HIPed materials but vary with different x values due to different phase contents. Measurements of cell parameters for all compositions show a continuous increase with increasing x value which is enhanced by high pressure at high x values.
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| 2. |
- Harrysson, Ralph, et al.
(författare)
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Energy distribution during laser machining of glass
- 1988
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Ingår i: Lasers in manufacturing. - : IFS. - 1854230212 - 3540503102 - 0387503102 ; , s. 25-34
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Konferensbidrag (refereegranskat)abstract
- Hole drilling of glass has been performed by use of a pulsed CO sub 2 laser of type Rofin Sinar RS 1500 in order to determine the best conditions for laser drilling. Relations have been established between the specific energy, the power density and the pulse time needed for drilling holes through glass plates of defined thicknesses. From these relationships it has been possible to decide the correct laser parameters for an optimized hole drilling with minimized crack formation
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| 4. |
- Harrysson, Ralph, et al.
(författare)
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Laser machining of HIP produced ceramics
- 1988
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Ingår i: HIP. - Luleå : CENTEK. - 918699834X ; , s. 389-393
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Konferensbidrag (refereegranskat)abstract
- HIP-produced high performance ceramics often need secondary machining. The investigation is concentrated on laser drilling of HIP-Si sub 3 N sub 4 and sialon using the single pulse technique. Experimental data give linear graphs for the specific energy vs. the pulse time and the power density vs. the inverse pulse time. The relationships are used for the construction of EP-diagrams, e.g. the relationship between specific energy and power density of the laser beam. From the EP-diagram can be found the energy consumption divided into different sources and different areas of machinability due to the power density
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