Wantanee Buggakupta

Effects of Diatomite and Glass Cullet in the Waste-Based Gypsum Building Materials

Gypsum building materials can be made from either natural resources or industrial residues. This work introduces the gypsum mixture based on domestic industrial wastes. The waste used as a calcium sulfate source in the mix is FGD gypsum from a power generation plant. Meanwhile, the silica-rich sources, i.e. diatomite, derived from brewery production, and soda-lime glass cullet from automotive safety glass industry are also employed. These wastes were pretreated before mixing and the compositions of the waste-based gypsum were carefully formulated and characterized. Phase presence and microstructural information were determined. Development in strength as well as water resistance was examined. The experimental work suggested that the addition of diatomite can significantly increase both strength and water insolubility.

Turning Electric Arc Furnace Dust Waste into Oil Spot Ceramic Glaze

Electric Arc Furnace (EAF) is commonly used in steel recycling industries. Apart from steel metal product, a waste in the form of dust is also produced and so called EAF dust. The fine particulates mainly contain zinc-iron oxides along with a small amount of heavy metals like chromium and lead, and have been categorized as a toxic waste. Proper treatments can be crucially required in order to recover crude zinc oxide and iron oxide from the dust; however, no practical recycling plants have been now readily operated in Thailand. To reduce its toxicity, EAF dust could be mixed with silica-based materials and vitrified into glass. Therefore, EAF dust can possibly be employed as a ceramic glaze raw material. This work pointed out how to make decorative “oil spot” ceramic glaze by substitution of EAF dust for a conventional iron oxide. The prepared glaze mixtures were applied over the ceramic bodies and fired at 1250 °C in oxidation atmosphere. The as-fired glaze appearances with tiny and silvery crystals floating over dark brown based-glaze were exhibited. Phase content and characteristics of the obtained glaze were analyzed. The roles of zinc oxide to iron oxide ratios on oil spot and crystal generation was concerned. A comparison of oil spot effects due to different iron oxide sources was presented and discussed. Oil spot glaze made from a combination of EAF dust and iron oxide powder was also proposed.

Effects of Water Temperatures on Water-Soluble Binder Removal in Ceramic Materials Fabricated by Powder Injection Moulding

This work focuses on the debinding conditions of the ceramic materials fabricated by powder injection moulding. Ceramic powder materials, including alumina and alumina-based composites were prepared as feedstocks and mixed with water-soluble polyethylene glycol (PEG) and polyvinyl butyral (PVB). The PEG/PVB binder mixture, with PEG to PVB ratio of 85:15 by weight and powder loading of 44 vol%, were thoroughly mixed and injected into the mould at the temperature of 190 °C to obtain rod-like specimens. Prior to sintering, the as-injected specimen was then leached in water, the temperature of which was varying from 30 (ambient temperature), 45 to 60 °C, in order to get rid of PEG and leave the specimens in shape by PVB. The rate of PEG removal according to different water temperatures was investigated. The experimental results suggested that PEG could completely be eliminated by 45 and 60 °C water without any dimensional disintegration in 5 hours whereas those leached in 30 °C water showed only 70% PEG removal. Higher water temperatures led to fast PEG removal rate at the beginning and then gradually decreased with elapsed times.

High Density Polyethylene Catalyst Waste as a Filler in Papermaking

The study observes the use of a waste derived from high density polyethylene (HDPE) catalyst production as fillers in papermaking. The replacement of the industrial waste to two common fillers; calcium carbonate and clay, are of interest. The waste is in the form of bright slurry containing very fine particulates with titanium dioxide, calcium oxide and alumina, along with a small amount of chlorides. As-received HDPE waste of 0-30 wt% was added into a mixture of pulp stock to make handsheets. Cationic polyacrylamide was employed as a retention aid. The obtained handsheet samples were then dried and their properties were characterized and also compared with the handsheets holding carbonate and clay. Such properties included both physical and mechanical ones, i.e. apparent density, air resistance, brightness, opacity, smoothness, tear and tensile strength. The experimental results showed that the as-received industrial waste gave comparable outcomes to carbonate and kaolin clay. Improvement of the handsheet properties with the HDPE catalyst waste was discussed.

Characteristics of Automotive Glass Waste-Containing Gypsum Bodies Made from Used Plaster Mould

This work focuses on characterization of gypsum building materials based on used plaster mould and automotive safety glass waste. The used plaster mould was another source of relatively high purity calcium sulfate. Meanwhile, automotive print-screened glass waste derived from glass machining processes and sedimented as a lump of glass powder was rich in silica. The used mould was ground and calcined in order to convert gypsum dihydrate into hemihydrate while the glass lump was dried and become loose cullet powder. The waste materials were thoroughly mixed and cast into blocks, using used plaster mould. Various glass waste contents from 0, 5, 10, 15 to 20 %wt were employed as a filler. Chemical compositions of the mix were carefully characterized. Phase content microstructural features were also determined. Development in compressive strength as well as water resistance were investigated. The experimental works showed that the addition of the glass waste in the used plaster mould containing gypsum bodies could comparatively improve both strength and water insolubility.

Effects of Waste from HDPE Catalyst Process on Melting Behaviour and Thermal Properties of White Opaque Glazes

Polyolefin catalyst wastes have been rising with growing high density polyethylene (HDPE) demand. Utilizing on recycling such waste residue has then become a challenging task to achieve. Due to its relatively fine particles, iron oxide-free and consistent composition, the waste can possibly be another alternative for ceramic glaze raw materials. This study observed the replacement of the waste to the conventional glaze raw materials. The residue mainly contains TiO2 along with CaO, Al2O3 and a small amount of chloride. Physical and chemical properties of the waste were characterized. The roles of the waste on melting behaviour and appearance were observed. Colour of the introduced waste-containing glaze was determined by a spectrophotometer. Finally, coefficient of linear thermal expansion of the obtained glazes was done by a dilatometer. Characteristics of the waste-bearing white opaque glazes were reported and discussed.

Role of Tungsten Carbide Reinforcement on Alumina Matrix Composites Fabricated by Powder Injection Moulding

In this work, properties of tungsten carbide (WC) particulate reinforced alumina matrix composites fabricated by powder injection moulding (PIM) technology were reported. The 90 wt% of Al2O3 and 10 wt% of WC powders were mixed with a composite binder, composed of 85 wt% polyethylene glycol (PEG) and 15 wt% polyvinyl butyral (PVB). Feedstocks of alumina and alumina-tungsten carbide composites having powder loading from 44 to 52 vol% were prepared and injected into a mould of rectangular shape. The binders in the mouldings were leached by water and then thermally debinded prior to sintering at 1600 °C for 2 hours in argon atmosphere. Strength, Density, hardness and density of the alumina and alumina composites’ bodies were compared and reported. It was found that the properties of sintered specimens, both Al2O3 and Al2O3/WC composites, increased with increasing powder loadings. The properties enhancement was also presented in the WC reinforced alumina composites. The composite of 52 vol% powder loading had flexural strength and hardness of 253.8 MPa and 12.5 GPa, respectively.

Influences of Cobalt and Zirconia on Microstructural Features and Mechanical Properties of the Al2O3/WC Composites

Alumina (Al2O3) is one of the most successful advanced ceramics due to its high hardness, chemical resistance as well as thermal stability under various severe operating conditions. Therefore, the Al2O3 and Al2O3 matrix composites were generally employed as cutting tool materials. The present work investigates an improvement in fracture toughness of the Al2O3-based composites reinforced by tungsten carbide (WC) particles. A change in toughness of the Al2O3/WC composites according to the additions of cobalt (Co) or partially stabilized zirconia (PSZ) is also of interest. The 90 wt% of Al2O3 and 10 wt% of WC powders, containing various amounts of Co or MgO-doped PSZ (Mg-PSZ), were formed by a conventional uniaxial pressing. The percentages of Co and Mg-PSZ were varied up to 3 and 4.5 wt%, respectively. The specimens were sintered in argon atmosphere at 1600 °C for 2 hours. The sintered specimens were subjected to testing and characterisation. The density was measured by water immersion method. Microstructure and phase analysis were investigated by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively. Vickers indentation technique was used to determine hardness and fracture toughness. Density of higher than 95% of the theoretical values could be achieved in all cases. The hardness values of the WC reinforced Al2O3 composites were higher than those of the monolithic Al2O3. The hardness of the composites did not change significantly with the Co addition but it gradually decreased with PSZ additions. However, the presence of both Co and PSZ led to slightly higher fracture toughness. The hardness and fracture toughness of the fabricated composites were in the range of 16-18 GPa and 5-8 MPa.m1/2, respectively, which were in the same ranges as commercial cutting tools currently used in the market.

Properties of Porous Alumina Fabricated by Ceramic Injection Moulding Using Environmentally Friendly Binder

Porous alumina (Al2O3) ceramics were fabricated by powder injection moulding process. The feedstocks, composed of 44 50 vol% of Al2O3 powder, could be prepared using a composite binder, consisting of polyethylene glycol (PEG) and polyvinyl butyral (PVB). Debindings were carried out using a combination of water leaching of the PEG and thermal debinding of the PVB. It was observed that the removal of the PEG was fast at the initial stage and more than 90 wt% of the PEG could be removed within 4 hours. Sintering was performed in argon atmosphere at 1600 °C. The sintered specimens had apparent porosity in range of 26-32 %, depending on the feedstock compositions. The flexural strength values were in range of 90-140 MPa while the hardness values were in range of 5-9 GPa. It was found that both the strength and hardness of the specimens were increased with increasing powder loading.

Mechanical Properties of Alumina Matrix Composites due to a Combination of Sr- and Ca-Hexaluminates

Alumina matrix composites have been successfully used in a wide range of applications for decades. Even alumina itself provides several desirable properties e.g. strength, chemical and thermal stability together with hardness, its toughness is still to be concerned. An addition of some intermediate phases such as alkali earth hexaluminates can enhance fracture toughness according to their unique morphology. This work investigated a variation in mechanical properties of alumina as a presence of two types of dispersed phases: strontium hexaluminate and calcium hexaluminate. The preformed hexaluminate compounds were prepared from a powder mixture of the alkali earth carbonates and alumina. The preformed hexaluminates were then added into alumina, followed by pressureless sintered at 1600 oC for 2 hours in air. A change in mechanical properties of alumina according to types and amount of additives as well as the ratio of calcium hexaluminate to strontium hexaluminate compounds on was studied. The composites with the relative density of at least 93%TD were achieved. Both hexaluminates resulted in a significant increase in fracture toughness relative to the monolithic alumina while they slightly affected on hardness and strength. When the ratio of calcium hexaluminate to strontium hexaluminate in alumina matrix was considered, a rise in fracture toughness strongly depended on the fraction of calcium hexaluinate. The calcium hexaluminate tended to be more efficient additive in order to strengthen alumina than that of the strontium ones