- Email: [email protected]
00836 Manufacturing of biomorphic (Si, Ti, Zr)-carbide ceramics by sol-gel processing
12 Refractories~ceramics (properties, production, applications) Recently, the authors developed Si3N4, A1203 and mullite ceramics with good self-crack-healing abilities. It was shown that the optimised crack-healing condition to get high t e m p e r a t u r e strength was: 1573 K, 1 h, in air, and the h e a l e d zone exhibited the same strength as the base m a t e r i a l up to about 1573 K (Si3N4 and A1203) and 1473 K (mullite), respectively. Using this good crack-healing ability, a new m e t h o d o l o g y to g u a r a n t e e the reliability of ceramic c o m p o n e n t s (crack-healing + proof test) was proposed. It was shown that reliability could be g u a r a n t e e d before service by this technique, using about 200 samples. However, if a crack initiated during service, reliability would be severely impaired. Therefore, if a m a t e r i a l can heal a crack during service, and if the h e a l e d zone has enough strength at the t e m p e r a t u r e of healing, it would be very desirable for structural integrity. F r o m the above points of view, a new m e t h o d o l o g y to g u a r a n t e e the structural integrity of ceramic c o m p o n e n t s using in situ crack-healing ability was proposed and the usefulness is discussed using the test results in terms of crack-healing behavior and proof test theory by the authors.
06/00833 Crack-healing behavior and resultant strength properties of silicon carbide ceramic Lee, S.-K. eta/. Journal of the European Ceramic Society, 2005, 25, (5), 569 576. Silicon carbide (SIC) has good high t e m p e r a t u r e strength and resistance to radioactivity. However, it has poor fracture toughness. To overcome this weakness, a crack-healing ability is very desirable. This study focuses on the crack-healing behaviour of commercial SiC ceramic. The crack-healing behaviours of SiC ceramic were investigated systematically, as a function of crack-healing temperature, time, crack size and t e m p e r a t u r e d e p e n d e n c e of the resultant bending strength. Three-point bending specimens were m a d e and a semielliptical crack was i n t r o d u c e d on the specimen by a Vickers indenter. Pre-cracked specimens were healed at various conditions. All fracture tests were performed on a three-point loading system with a 16 m m b e n d i n g span. The main conclusions obtained were: (1) optimized crack-healing condition is; temperature: 1773 K, 1 h in air. (2) The m a x i m u m crack size that can be healed completely under the optimized condition was semi-elliptical surface crack of 450 m m in diameter. (3) Limiting t e m p e r a t u r e for b e n d i n g strength of crack-healed zone for b e n d i n g strength was about 873 K.
06•00834 Effects of double glazed facade on energy consumption, thermal comfort and condensation for a typical office building in Singapore Wong, N. H. eta/. Energy and Buildings, 2005, 37, (6), 563 572. Fully glazed facade that has been increasingly used in Singapore causes higher energy c o n s u m p t i o n and t h e r m a l discomfort due to higher solar gain. The use of double glazed facade system with ventilation system is one way to solve these problems. The objective of this paper is to investigate the effects of double glazed facade with ventilation system on the energy consumption, t h e r m a l comfort and condensation and c o m p a r e to single glazed facade system. TAS and C F D software were utilized to calculate energy consumption, t h e r m a l comfort and condensation for single glazed facade building as well as double glazed facade building. The simulation results showed double glazed facade with natural ventilation were able to minimize energy c o n s u m p t i o n as well as to enhance the t h e r m a l comfort. Turning the mechanical fans on could also solve the condensation problem due to high humidity.
06/00835 Energy performance assessment of a window with a horizontal Venetian blind Shahid, H. and Naylor, D. Energy and Buildings, 2005, 37, (8), 836 843. This study examines the effects of the presence of a venetian blind on the t h e r m a l performance of a window. The blind is positioned adjacent to the indoor surface of either a single or double glazed window and the coupled convection and radiation heat transfer problem is solved using a two-dimensional finite v o l u m e model. The numerical model is validated with published e x p e r i m e n t a l and n u m e r i c a l results in the literature. The results show that the presence of a venetian blind significantly improves the energy performance of a single and double glazed window. The blind reduces the overall heat transfer rate through the window by reducing the t h e r m a l radiation from the indoor glazing. The improved u n d e r s t a n d i n g of the benefits of venetian blinds may lead to better designs of window/shading systems.
06/00836 Manufacturing of biomorphic (Si, Ti, Zr)-carbide ceramics by sol-gel processing R a m b o , C. R. eta/. Carbon, 2005, 43, (6), 1174 1183. B i o m o r p h i c (wood derived) carbide ceramics with an overall composition in the systems M e C / C (with Me = Si, Ti, Zr) were produced by v a c u u m infiltration of low viscosity organo-metallic colloidal suspensions into biologically derived carbon templates. After hydrolysis into Me(OH)4-gels, the Me(OH)4-gel/C-templates were s u b m i t t e d to a high t e m p e r a t u r e pyrolysis/reaction t r e a t m e n t at 1600:C to p r o m o t e (i) the polycondensation of the Me(OH)4-gels into the corresponding MeO2-
phase and (ii) the c a r b o t h e r m a l reaction of the MeO2 with the biocarbon template into highly porous, b i o m o r p h i c SiC/C-, TiC/C- and ZrC/C-ceramics. The influence of the initial porosity of the biocarbon template on the final phase composition and m o r p h o l o g y of the formed b i o m o r p h i c M e C / C - c e r a m i c composites is analysed.
06/00837 Near net-shape fabrication of alumina glass composites Zhu, Q. et al. Journal of the European Ceramic Society, 2005, 25, (5), 633 638. The purpose of the present study is to fabricate a l u m i n a glass composites by melt infiltration with better d i m e n s i o n a l control through reducing both the presintering and infiltration temperature. Main efforts were put to develop glasses that are chemically compatible with alumina. After extensive investigations, a glass of 21SiO2 24B203 35A1203 15Li20 5CaO wt% was successfully developed. The glass shows good chemical compatibility with a l u m i n a at elevated temperatures and low viscosity above 900:C. Dense a l u m i n a glass composites can be fabricated by the m e l t infiltration process at 950:C, which is 150:C lower than the current state-of-art. Investigations showed improved net-shape capability for the newly developed composites, where the total linear shrinkage for the sintering and infiltration at 950:C is less than 0.1%,, as c o m p a r e d with the shrinkage of 0.5%, induced by the presintering and infiltration at l l 0 0 : C . Preliminary mechanical tests showed that the fracture strength and toughness of the composites are 303 M P a and 3.4 M P a m 1/2, respectively. The lower processing t e m p e r a t u r e and the better d i m e n s i o n a l control are the major advantages for the newly developed a l u m i n a glass composites.
06/00838 Performance rating of glass windows and glass windows with films in aspect of thermal comfort and heat transmission Chaiyapinunt, S. et al. Energy and Buildings, 2005, 37, (7), 725 738. This article is about a study on glass window and glass window with film of different types in aspect of t h e r m a l comfort and heat transmission. Different types of glass window, clear glass, tinted glass, reflective glass, double pane glass, and low-e glass were investigated. Films with different spectral optical properties were then adhered to the glass windows of different types and studied. The analysis was done based on the outside design weather condition which selected from 12 years of B a n g k o k meteorological data. Predicted percentage of dissatisfied (PPD) was selected as the thermal comfort index. The relative heat gain ( R H G ) based on local weather condition was selected as the heat transmission index. The PPD can be subdivided into the PPD due to surface temperature effect and the PPD due to solar r a d i a t i o n effect. The analysis indicated that, for most of the glass windows considered except the reflective glasses, the values of PPD due to solar r a d i a t i o n effect were much larger than the values of PPD due to surface temperature effect. A n d the most discomfort condition occurred when using a clear glass as window. Adhered films to the glass windows caused the PPD due to surface temperature effect increase and cause the PPD due to solar r a d i a t i o n effect decrease. It was also found that the PPD values due to solar r a d i a t i o n effect for glass windows and glass windows with films were varied linearly with the total transmittance of glass windows and glass windows with films. The PPD values due to surface temperature effect were varied with the total absorptance of glass windows and glass windows with films in an almost linear fashion. The heat transmission index, R H G , based on chosen design weather condition can be subdivided into the R H G due to conduction effect and R H G due to solar r a d i a t i o n effect. The analysis indicated that the values of R H G due to solar r a d i a t i o n effect were larger than the values of R H G due to conduction effect for all glass windows and glass windows with films considered in this study. A d h e r e d film to the glass windows resulted in lowering the relative heat gain due to solar r a d i a t i o n in the a m o u n t corresponding to the film properties. But the film had very few effects on the relative heat gain due to conduction. The relative heat gain values were varied linearly with the total transmittances of the glass windows and glass windows with films. The relative heat gain values were also varied inversely with the absorptances of glass windows and glass windows with films in a linear fashion.
06/00839 Windows in the workplace: examining issues of environmental sustainability and occupant comfort in the selection of multi-glazed windows Menzies, G. F. and W h e r r e t t , J. R. Energy and Buildings, 2005, 37, (6), 623 630. Windows are i m p o r t a n t in the workplace for both e n v i r o n m e n t a l and psychological reasons. G o o d glazing design can reduce energy outputs by lowering the r e q u i r e m e n t s for heating or cooling; frame design can utilize more sustainable materials and those with lower e m b o d i e d energy, such as timber and aluminium-clad timber. Windows are also i m p o r t a n t for the provision of daylight and a view, both of which have known psychological benefits, although glare and passive solar gain can
Fuel and Energy Abstracts
March 2006
123
06/00833 Crack-healing behavior and resultant strength properties of silicon carbide ceramic Lee, S.-K. eta/. Journal of the European Ceramic Society, 2005, 25, (5), 569 576. Silicon carbide (SIC) has good high t e m p e r a t u r e strength and resistance to radioactivity. However, it has poor fracture toughness. To overcome this weakness, a crack-healing ability is very desirable. This study focuses on the crack-healing behaviour of commercial SiC ceramic. The crack-healing behaviours of SiC ceramic were investigated systematically, as a function of crack-healing temperature, time, crack size and t e m p e r a t u r e d e p e n d e n c e of the resultant bending strength. Three-point bending specimens were m a d e and a semielliptical crack was i n t r o d u c e d on the specimen by a Vickers indenter. Pre-cracked specimens were healed at various conditions. All fracture tests were performed on a three-point loading system with a 16 m m b e n d i n g span. The main conclusions obtained were: (1) optimized crack-healing condition is; temperature: 1773 K, 1 h in air. (2) The m a x i m u m crack size that can be healed completely under the optimized condition was semi-elliptical surface crack of 450 m m in diameter. (3) Limiting t e m p e r a t u r e for b e n d i n g strength of crack-healed zone for b e n d i n g strength was about 873 K.
06•00834 Effects of double glazed facade on energy consumption, thermal comfort and condensation for a typical office building in Singapore Wong, N. H. eta/. Energy and Buildings, 2005, 37, (6), 563 572. Fully glazed facade that has been increasingly used in Singapore causes higher energy c o n s u m p t i o n and t h e r m a l discomfort due to higher solar gain. The use of double glazed facade system with ventilation system is one way to solve these problems. The objective of this paper is to investigate the effects of double glazed facade with ventilation system on the energy consumption, t h e r m a l comfort and condensation and c o m p a r e to single glazed facade system. TAS and C F D software were utilized to calculate energy consumption, t h e r m a l comfort and condensation for single glazed facade building as well as double glazed facade building. The simulation results showed double glazed facade with natural ventilation were able to minimize energy c o n s u m p t i o n as well as to enhance the t h e r m a l comfort. Turning the mechanical fans on could also solve the condensation problem due to high humidity.
06/00835 Energy performance assessment of a window with a horizontal Venetian blind Shahid, H. and Naylor, D. Energy and Buildings, 2005, 37, (8), 836 843. This study examines the effects of the presence of a venetian blind on the t h e r m a l performance of a window. The blind is positioned adjacent to the indoor surface of either a single or double glazed window and the coupled convection and radiation heat transfer problem is solved using a two-dimensional finite v o l u m e model. The numerical model is validated with published e x p e r i m e n t a l and n u m e r i c a l results in the literature. The results show that the presence of a venetian blind significantly improves the energy performance of a single and double glazed window. The blind reduces the overall heat transfer rate through the window by reducing the t h e r m a l radiation from the indoor glazing. The improved u n d e r s t a n d i n g of the benefits of venetian blinds may lead to better designs of window/shading systems.
06/00836 Manufacturing of biomorphic (Si, Ti, Zr)-carbide ceramics by sol-gel processing R a m b o , C. R. eta/. Carbon, 2005, 43, (6), 1174 1183. B i o m o r p h i c (wood derived) carbide ceramics with an overall composition in the systems M e C / C (with Me = Si, Ti, Zr) were produced by v a c u u m infiltration of low viscosity organo-metallic colloidal suspensions into biologically derived carbon templates. After hydrolysis into Me(OH)4-gels, the Me(OH)4-gel/C-templates were s u b m i t t e d to a high t e m p e r a t u r e pyrolysis/reaction t r e a t m e n t at 1600:C to p r o m o t e (i) the polycondensation of the Me(OH)4-gels into the corresponding MeO2-
phase and (ii) the c a r b o t h e r m a l reaction of the MeO2 with the biocarbon template into highly porous, b i o m o r p h i c SiC/C-, TiC/C- and ZrC/C-ceramics. The influence of the initial porosity of the biocarbon template on the final phase composition and m o r p h o l o g y of the formed b i o m o r p h i c M e C / C - c e r a m i c composites is analysed.
06/00837 Near net-shape fabrication of alumina glass composites Zhu, Q. et al. Journal of the European Ceramic Society, 2005, 25, (5), 633 638. The purpose of the present study is to fabricate a l u m i n a glass composites by melt infiltration with better d i m e n s i o n a l control through reducing both the presintering and infiltration temperature. Main efforts were put to develop glasses that are chemically compatible with alumina. After extensive investigations, a glass of 21SiO2 24B203 35A1203 15Li20 5CaO wt% was successfully developed. The glass shows good chemical compatibility with a l u m i n a at elevated temperatures and low viscosity above 900:C. Dense a l u m i n a glass composites can be fabricated by the m e l t infiltration process at 950:C, which is 150:C lower than the current state-of-art. Investigations showed improved net-shape capability for the newly developed composites, where the total linear shrinkage for the sintering and infiltration at 950:C is less than 0.1%,, as c o m p a r e d with the shrinkage of 0.5%, induced by the presintering and infiltration at l l 0 0 : C . Preliminary mechanical tests showed that the fracture strength and toughness of the composites are 303 M P a and 3.4 M P a m 1/2, respectively. The lower processing t e m p e r a t u r e and the better d i m e n s i o n a l control are the major advantages for the newly developed a l u m i n a glass composites.
06/00838 Performance rating of glass windows and glass windows with films in aspect of thermal comfort and heat transmission Chaiyapinunt, S. et al. Energy and Buildings, 2005, 37, (7), 725 738. This article is about a study on glass window and glass window with film of different types in aspect of t h e r m a l comfort and heat transmission. Different types of glass window, clear glass, tinted glass, reflective glass, double pane glass, and low-e glass were investigated. Films with different spectral optical properties were then adhered to the glass windows of different types and studied. The analysis was done based on the outside design weather condition which selected from 12 years of B a n g k o k meteorological data. Predicted percentage of dissatisfied (PPD) was selected as the thermal comfort index. The relative heat gain ( R H G ) based on local weather condition was selected as the heat transmission index. The PPD can be subdivided into the PPD due to surface temperature effect and the PPD due to solar r a d i a t i o n effect. The analysis indicated that, for most of the glass windows considered except the reflective glasses, the values of PPD due to solar r a d i a t i o n effect were much larger than the values of PPD due to surface temperature effect. A n d the most discomfort condition occurred when using a clear glass as window. Adhered films to the glass windows caused the PPD due to surface temperature effect increase and cause the PPD due to solar r a d i a t i o n effect decrease. It was also found that the PPD values due to solar r a d i a t i o n effect for glass windows and glass windows with films were varied linearly with the total transmittance of glass windows and glass windows with films. The PPD values due to surface temperature effect were varied with the total absorptance of glass windows and glass windows with films in an almost linear fashion. The heat transmission index, R H G , based on chosen design weather condition can be subdivided into the R H G due to conduction effect and R H G due to solar r a d i a t i o n effect. The analysis indicated that the values of R H G due to solar r a d i a t i o n effect were larger than the values of R H G due to conduction effect for all glass windows and glass windows with films considered in this study. A d h e r e d film to the glass windows resulted in lowering the relative heat gain due to solar r a d i a t i o n in the a m o u n t corresponding to the film properties. But the film had very few effects on the relative heat gain due to conduction. The relative heat gain values were varied linearly with the total transmittances of the glass windows and glass windows with films. The relative heat gain values were also varied inversely with the absorptances of glass windows and glass windows with films in a linear fashion.
06/00839 Windows in the workplace: examining issues of environmental sustainability and occupant comfort in the selection of multi-glazed windows Menzies, G. F. and W h e r r e t t , J. R. Energy and Buildings, 2005, 37, (6), 623 630. Windows are i m p o r t a n t in the workplace for both e n v i r o n m e n t a l and psychological reasons. G o o d glazing design can reduce energy outputs by lowering the r e q u i r e m e n t s for heating or cooling; frame design can utilize more sustainable materials and those with lower e m b o d i e d energy, such as timber and aluminium-clad timber. Windows are also i m p o r t a n t for the provision of daylight and a view, both of which have known psychological benefits, although glare and passive solar gain can
Fuel and Energy Abstracts
March 2006
123