scholarly journals Alumina ceramics prepared with new pore-forming agents

2008 ◽  
Vol 2 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Zuzana Zivcová ◽  
Eva Gregorová ◽  
Willi Pabst
Keyword(s):  
Thermal Analysis ◽  
Porous Alumina ◽  
Slip Casting ◽  
Porous Ceramics ◽  
Rice Starch ◽  
Alumina Ceramics ◽  
Poppy Seed ◽  
Biological Origin ◽  
Filtration Membranes ◽  
Wide Range

Porous ceramics have a wide range of applications at all length scales, ranging from filtration membranes and catalyst supports to biomaterials (scaffolds for bone ingrowths) and thermally or acoustically insulating bulk materials or coating layers. Organic pore-forming agents (PFAs) of biological origin can be used to control porosity, pore size and pore shape. This work concerns the characterization and testing of several less common pore-forming agents (lycopodium, coffee, fl our and semolina, poppy seed), which are of potential interest from the viewpoint of size, shape or availability. The performance of these new PFAs is compared to that of starch, which has become a rather popular PFA for ceramics during the last decade. The PFAs investigated in this work are in the size range from 5 ?m (rice starch) to approximately 1 mm (poppy seed), all with more or less isometric shape. The burnout behavior of PFAs is studied by thermal analysis, i.e. thermogravimetry and differential thermal analysis. For the preparation of porous alumina ceramics from alumina suspensions containing PFAs traditional slip casting (into plaster molds) and starch consolidation casting (using metal molds) are used in this work. The resulting microstructures are investigated using optical microscopy, combined with image analysis, as well as other methods (Archimedes method of double-weighing in water, mercury intrusion porosimetry).

Fabrication of Al2O3 Ceramics by Environmentally Friendly Process

2006 ◽  
Vol 317-318 ◽  
pp. 751-754
Author(s):  
Takaaki Nagaoka ◽  
Takahisa Tsugoshi ◽  
Yuji Hotta ◽  
Kimiyasu Sato ◽  
Koji Watari
Keyword(s):  
Evolved Gas Analysis ◽  
Porous Alumina ◽  
Environmentally Friendly ◽  
Gas Analysis ◽  
Fabrication Process ◽  
Alumina Ceramics ◽  
Pore Size Distributions ◽  
Wide Range ◽  
Added Water ◽  
Α Al2o3

We have developed a new environmentally friendly fabrication process for alumina ceramics using hydraulic alumina (HA) and water. Without the addition of an organic binder, alumina green bodies retained their original shapes by the hydration of HA in the green bodies. In the case of α-Al2O3-HA-H2O system, alumina ceramics with 97.8% theoretical density were obtained. Added water acted as a fugitive material in the hardened green body. In the case of HA-H2O system, porous alumina ceramics with a wide range of open porosity (56.6–69.1%) and narrow pore size distributions were fabricated without the use of organic fugitive materials. The results of evolved gas analysis-mass spectrometry measurements showed that the new fabrication process for alumina ceramics was confirmed to be eco-friendly.

scholarly journals Augsti poraina oksīdu keramika

2018 ◽  
Vol 35 ◽  
pp. 86-111
Author(s):  
Visvaldis Švinka ◽  
Ruta Švinka
Keyword(s):  
High Temperature ◽  
Thermal Shock ◽  
Raw Materials ◽  
Porous Alumina ◽  
Slip Casting ◽  
Carbon Oxide ◽  
Porous Ceramics ◽  
Basic Medium ◽  
Oxide Systems ◽  
Synthesis Conditions

Silikātu materiālu institūtā kopš 2004. g. tiek veikti pētījumi par augsttemperatūras augsti porainu oksīdu keramiku, kas iegūta ar koncentrētas oksīdu pulveru suspensijas liešanas paņēmienu. Poru veidošanās notiek ķīmiskas reakcijas ceļā starp metāliska alumīnija pulveri un ūdeni bāziskā vidē, kur suspensijas pH ir 9,5–10,8. Tādā veidā netiek emitēts CO2, kas parasti notiek, iegūstot keramikas materiālus ar paaugstinātu porainību.Laikā kopš 2007. g. sintezēti materiāli un veikti pētījumi vairākās augsttemperatūras oksīdu sistēmās: cirkonija oksīdu saturošā (promocijas darbs, G. Buļa, Cirkonija oksīdu saturoša augsttemperatūras putu keramika, 2008. g.), korunda- mullīta sistēmā (promocijas darbs, L. Mahņicka-Goremikina, Sintēzes apstākļu un leģējošu piedevu ietekme uz porainas augsttemperatūras oksīdu keramikas īpašībām un struktūru, 2015. g.), alumīnija oksīda sistēmā ar dažādām piedevām (promocijas darbs, I. Zaķe-Tiļuga. Mullītu veidojošu piedevu ietekme uz porainas alumīnija oksīda keramikas īpašībām, 2015. g.; nepabeigts promocijas darbs A. Butlers, Karstumizturīga filtrējoša keramika; maģistra darbs, J. Bobrovika, Augsti poraina siltumizolējoša kordierīta keramika). Pētītie materiāli paredzēti, lai izmantotu tos kā siltumizolējošus materiālus dažādām augsttemperatūras siltuma ierīcēm un arī karstumizturīgiem filtriem.Highly Porous Oxide CeramicsInvestigations of highly porous high temperature ceramic produced by slip casting from concentrated suspensions of raw materials were carried out in the Institute of Silicate Materials since 2004. Pores form due to chemical reaction of metallic aluminium powder with water in basic medium with pH 9.5–10.8. Using this method emission of carbon oxide that usually accompanies fabrication of porous ceramics is avoided. The following investigations in high temperature oxide systems have been carried out since 2007:zirconia containing materials – promotion work by Gerda Bula “Zircon oxide containing high temperature foam ceramic”, 2008;corundum–mullite materials – promotion work by Ludmila Mahnicka- Goremikina “Influence of synthesis conditions and additives on the structure and properties of porous high temperature ceramics”, 2015;alumina materials with various additives – promotion work by Ieva Zake-Tiluga “The effect of mullite-forming additives on the properties of porous alumina ceramics”, 2015;titania containing corundum–mullite materials;cordierite ceramic materials.The goals of these investigations were to obtain of high temperature insulating materials and ceramic filters for filtration of hot and aggressive liquids. Properties of ceramics, such as dependence of thermal conductivity on the temperature and thermal shock durability, were determined.Keywords: aluminium oxide, zirconium oxide, titanium oxide, kaolin, talcum, cordierite, nanopowders, thermal insulation, thermal shock resistance.

scholarly journals Modification of Porous Alumina Ceramics with Bioinert and Bioactive Glass Coatings

2008 ◽  
Vol 32 ◽  
pp. 211-214 ◽  
Author(s):  
X. Miao
Keyword(s):  
Bioactive Glass ◽  
Porous Alumina ◽  
Porous Ceramics ◽  
Glass Layer ◽  
Alumina Ceramics ◽  
Tissue Replacement ◽  
Porous Biomaterials ◽  
Porous Bioceramics ◽  
Pu Foams ◽  
Zirconia Addition

Porous biomaterials including porous bioceramics play important roles for hard tissue replacement and regeneration. I this paper, porous alumina (with and without zirconia addition) ceramics were produced via coating polyurethane (PU) foams with Al2O3 (ZrO2) slurries, followed by drying at room temperature and sintering at 1300 oC. The advantage of the PU foam method was the achieved high pore interconnectivity, but the mechanical properties of the porous ceramics were rather poor due to the high macroporosity and the high microporosity. To remove the microporosity and strengthen the porous alumina ceramics, a lanthanum-modified aluminosilicate (LAS) glass was used to infiltrate the alumina struts. Nevertheless, the resulting LAS-modified macroporous alumina ceramics would have no ability to bond to bone tissues. To impart a bioactivity (i.e. the ability of bone bonding) to the bioinert porous ceramics, a bioactive glass layer was applied by dipping with the bioactive glass slurry and sintering at 1200 oC. The twice coated porous alumina ceramics would exhibit high compressive strengths, allow bone tissue ingrowth, and form strong bonematerial integration. A biodegradable filler – calcium phosphate cement was also incorporated. A possible application of the porous bioceramics would be for the maxillofacial reconstruction.

Porous alumina ceramics for slip casting molds

1995 ◽  
Vol 1 (1) ◽  
pp. 69-74 ◽  
Author(s):  
Yoshihito Kondo ◽  
Yutaka Hashizuka ◽  
Shojiro Okada ◽  
Kozo Ishizaki
Keyword(s):  
Porous Alumina ◽  
Slip Casting ◽  
Alumina Ceramics

Porous Ceramics Obtained by Slip/Starch Casting Consolidation Method (SSCC)

2016 ◽  
Vol 881 ◽  
pp. 52-57
Author(s):  
Rodrigo Sampaio Fernandes ◽  
Elson de Campos ◽  
Jerusa Góes Aragão Santana ◽  
Rogério Pinto Mota
Keyword(s):  
Slip Casting ◽  
Porous Ceramics ◽  
Mechanical Resistance ◽  
Alumina Ceramics ◽  
Forming Process ◽  
Porous Mold ◽  
Different Characteristics ◽  
Starch Consolidation ◽  
Resistance Value ◽  
Gelling Process

Slip/starch casting consolidation (SSCC) is a technique for obtaining porous ceramics, which joins the forming process by starch consolidation with the slip casting method. In this work, a slip which contains ceramic powders, starch and dispersant, is poured into a porous mold and is taken to an oven so that the gelling process occurs. After sintering, it is noticed that the ceramics show different characteristics from the ones obtained exclusively by slip casting or by starch consolidation. Alumina ceramics were produced by using the three methods presented in this work. The ceramics were characterized by apparent porosity, mechanical resistance and scanning electron microscopy. The ceramics produced by SSCC presented the highest mechanical resistance value (289 MPa), while the ones produced by starch consolidation and slip casting presented values of 126 MPa and 191 MPa, respectively.

Anisotropy of Compressive Strength in Porous Alumina Ceramics

2014 ◽  
Vol 604 ◽  
pp. 153-156 ◽  
Author(s):  
Ieva Zake-Tiluga ◽  
Ruta Svinka ◽  
Visvaldis Svinka
Keyword(s):  
Compressive Strength ◽  
Sintering Temperature ◽  
Porous Alumina ◽  
Slip Casting ◽  
Mechanical Anisotropy ◽  
Alumina Ceramics ◽  
Casting Method ◽  
Concrete Technology ◽  
Pore Former ◽  
Aerated Concrete

Anisotropy of the compressive strength was investigated in porous alumina based ceramics produced by slip casting method. Aluminium paste was used as pore former similarly as in the aerated concrete technology. Materials were sintered at 1650°C and 1750°C. The apparent porosity of the investigated materials was in the range of 54±1% to 60±2%. The compressive strength of the samples in the directions parallel and perpendicular to the sample expansion direction was in the range from 3.8±0.3 to 13.0±1.1 MPa and from 6.4±1.3 to 27.0±1.1 MPa, respectively. The mechanical anisotropy was related with the flattening of the introduced pores. The level of mechanical anisotropy was affected by the initial composition of the slurry and sintering temperature.

Processing and Microstructural Characterization of Porous Alumina-Zirconia Ceramic Using CMC and PVC

2008 ◽  
Vol 591-593 ◽  
pp. 510-513 ◽  
Author(s):  
Ana Coh O. Hirschmann ◽  
Maria do Carmo de Andrade Nono ◽  
R.R. Riehl ◽  
C.R.M. Silva
Keyword(s):  
Porous Alumina ◽  
Porous Ceramic ◽  
Microstructural Characterization ◽  
Porous Ceramics ◽  
Zirconia Ceramic ◽  
Ceramic Filters ◽  
Pore Sizes ◽  
Wide Range ◽  
Materials Used ◽  
Organic Particles

Porous materials are of significant interest due to their wide application in catalysis, separation, lightweight structural materials, biomaterials and other areas. Porous ceramics are produced within a wide range of porosities and pore sizes depending on the application intended. Porosity and pore size distribution can be carefully controlled by the choice of organic composite and the amount added. The material may have two types of pores: open and closed pores. The open pores, also called interconnected pores, are those which are in contact with the external surface of the material, being very useful for the manufacture of ceramic filters. A high number of closed pores are important for the manufacturing of materials used in thermal applications. There are many methods for obtaining porous ceramics, in general consisting in adding to the ceramic matrix organic particles, which volatilize during the first heat-up. The objective of this study was to produce ceramic composite nanostructure of alumina and yttria stabilized zirconia (Y-TZP) with micrometric pore sizes. The effects of ZrO2 additions in the mechanical properties of Al2O3 have been intensively investigated, due to the possible increase of the mechanical strength of this material. The organic particles used to create the pores were CMC and PVC. The microstructure of the porous ceramic samples obtained was evaluated considering the degree of sinterization of the nanoparticles, pores formation, porosity, specific surface of the pores and the distribution of the interconnecting pores.

scholarly journals High-strength porous alumina ceramics prepared from stable wet foams

2021 ◽  
Author(s):  
Linying Wang ◽  
Liqiong An ◽  
Jin Zhao ◽  
Shunzo Shimai ◽  
Xiaojian Mao ◽  
...  
Keyword(s):  
Heat Insulation ◽  
Porous Alumina ◽  
High Strength ◽  
Porous Ceramics ◽  
High Porosity ◽  
Alumina Ceramics ◽  
Direct Foaming ◽  
Catalyst Carrier ◽  
Average Grain Size ◽  
Direct Foaming Method

AbstractPorous ceramics have been widely used in heat insulation, filtration, and as a catalyst carrier. Ceramics with high porosity and high strength are desired; however, this high porosity commonly results in low strength materials. In this study, porous alumina with high porosity and high strength was prepared by a popular direct foaming method based on particle-stabilized wet foam that used ammonium polyacrylate (PAA) and dodecyl trimethyl ammonium chloride (DTAC) as the dispersant and hydrophobic modifier, respectively. The effects of the dispersant and surfactant contents on the rheological properties of alumina slurries, stability of wet foams, and microstructure and mechanical properties of sintered ceramics were investigated. The microstructure of porous ceramics was regulated using wet foams to achieve high strength. For a given PAA content, the wet foams exhibited increasing stability with increasing DTAC content. The most stable wet foam was successfully obtained with 0.40 wt% PAA and 0.02 wt% DTAC. The corresponding porous alumina ceramics had a porosity of 82%, an average grain size of 0.7 µm, and a compressive strength of 39 MPa. However, for a given DTAC content, the wet foams had decreasing stability with increasing PAA content. A possible mechanism to explain these results is analyzed.

scholarly journals Optimization of Sintering Process of Alumina Ceramics Using Response Surface Methodology

2021 ◽  
Vol 13 (12) ◽  
pp. 6739
Author(s):  
Darko Landek ◽  
Lidija Ćurković ◽  
Ivana Gabelica ◽  
Mihone Kerolli Mustafa ◽  
Irena Žmak
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Heating Rate ◽  
Sintering Temperature ◽  
Nonlinear Models ◽  
Slip Casting ◽  
Holding Time ◽  
Alumina Ceramics ◽  
Aqueous Suspensions ◽  
Temperature Heating

In this work, alumina (Al2O3) ceramics were prepared using an environmentally friendly slip casting method. To this end, highly concentrated (70 wt.%) aqueous suspensions of alumina (Al2O3) were prepared with different amounts of the ammonium salt of a polycarboxylic acid, Dolapix CE 64, as an electrosteric dispersant. The stability of highly concentrated Al2O3 aqueous suspensions was monitored by viscosity measurements. Green bodies (ceramics before sintering) were obtained by pouring the stable Al2O3 aqueous suspensions into dry porous plaster molds. The obtained Al2O3 ceramic green bodies were sintered in the electric furnace. Analysis of the effect of three sintering parameters (sintering temperature, heating rate and holding time) on the density of alumina ceramics was performed using the response surface methodology (RSM), based on experimental data obtained according to Box–Behnken experimental design, using the software Design-Expert. From the statistical analysis, linear and nonlinear models with added first-order interaction were developed for prediction and optimization of density-dependent variables: sintering temperature, heating rate and holding time.

Thermal analysis method of electromagnetic linear actuator based on multiphysics coupling model

2021 ◽  
pp. 1-17
Author(s):  
Geng Wang ◽  
Renjing Gao ◽  
Qi Wang ◽  
Shutian Liu
Keyword(s):  
Thermal Analysis ◽  
Thermal Characteristics ◽  
Coupling Model ◽  
Analysis Method ◽  
Thermal Analysis Method ◽  
Performance Requirements ◽  
Wide Range ◽  
Multiphysics Coupling ◽  
Simulation And Experiment ◽  
Electromagnetic Linear Actuator

Electromagnetic linear actuators (ELAs) may be confronted with unsatisfactory performance when subjected to overheating. Therefore, it is significant to clarify its thermal characteristics and design the thermal performance requirements. A thermal analysis method based on multiphysics coupling model was presented, which uses the non-simplified loss distribution as the heat source to calculate the temperature field, adjusts the material properties by temperature, and considers the interaction between motion (including impact) and loss. More importantly, an improved universal equivalent winding to satisfy the condition of real compact concentrated winding was developed. Finally, the validity of this approach was verified through the experiment, and the regularity of temperature was summarized. The results show that the error of simulation and experiment is less than 6% and the permissible continuous operation frequency is no more than 30 Hz. The approach proposed in this paper can be employed not only to the ELA, but also to the design and analysis a wide range of electromagnetic machines.

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