Synthesis of Spinel-Hydroxyapatite Composite Utilizing Bovine Bone and Beverage Can

Spinel-based hydroxyapatite composite (SHC) has been synthesized utilizing bovine bones as the source of the hydroxyapatite (HAp) and beverage cans as the aluminum (Al) source. The bovine bones were defatted and calcined in the air atmosphere to transform them into hydroxyapatite. The beverage cans were cut and milled to obtain fine Al powder and then sieved to obtain three different particle mesh size fractions: +100#, −140# + 170#, and −170#, or Al particle size of >150, 90–150, and <90 µm, respectively. The SHC was synthesized using the self-propagating intermediate-temperature synthesis (SIS) method at 900 °C for 2 h with (HAp:Al:Mg) ratio of (87:10:3 wt.%) and various compaction pressure of 100, 171, and 200 MPa. It was found that the mechanical properties of the SHC are influenced by the Al particle size and the compaction pressure. Smaller particle size produces the tendency of increasing the hardness and reducing the porosity of the composite. Meanwhile, increasing compaction pressure produces a reduction of the SHC porosity. The increase in the hardness is also observed by increasing the compaction pressure except for the smallest Al particle size (<90 µm), where the hardness instead becomes smaller.

SHOCK-WAVE INITIATION OF SYNTHESIS IN NI-AL POWDER MIXTURE INSIDE TITANIUM MATRIX

This study presents the results of studying the effect of shock-wave loading on the initiation of synthesis in Ni-Al powder mixture inside titanium matrix. X-ray phase analysis (XRD) and measurement of the microhardness of the intermetallic layer showed that this layer consists of a monophase product NiAl, which is formed directly during explosive loading at a given impact velocity of the plate. Thus, the use of shock-wave loading made it possible to obtain a layered material with a strengthening intermetallic layer. The results obtained are promising for the development of new structural materials with special performance properties.

Application of Copper as Stabiliser in Aluminium Assisted Transfer of Titanium in Submerged Arc Welding of Carbon Steel

The element transfer of Ti from molten flux to the weld metal is limited to less than 310 ppm Ti in the submerged arc welding of carbon steel. This limitation is due to the high oxygen partial pressure prevailing at the molten flux-weld pool interface. Our previous study illustrated that the use of Al powder in combination with Ti powder improves the transfer of Ti to the weld metal to 4% Ti, whilst maintaining 509 ppm O in the weld metal. The weld metal ppm O should be controlled at 200 to 500 ppm O to maintain weld metal toughness. In this study, the addition of Cu powder with Ti and Al powder is applied to illustrate the stabiliser effect of Cu in the weld pool. The role of Cu as weld pool stabiliser is due to its decrease of the temperature required to melt Ti into the weld pool, so increasing the quantity of metal powder melted into the weld pool. The weld metal composition improved to 5.1% Ti, 3.6% Cu, and 371 ppm O. Thus, the role of Al in controlling the partial oxygen pressure at the molten flux-weld pool interface is maintained in the presence of Cu powder.

Determination of the Influence of Hydraulic Additives on the Foaming Process and Stability of the Produced Geopolymer Foams

The research described in this article was aimed at determining the influence of hydraulic additives on the foaming process and the stability of the produced geopolymer foams. These foams can be used as insulation materials to replace the currently commonly used insulations such as expanded polystyrene or polyurethane foams. Geopolymers have low thermal conductivity, excellent fire- and heat-resistant properties, and have fairly good mechanical properties. Research on foamed materials shows that they have the highest class of fire resistance; therefore, they are most often used as insulation products in construction. Geopolymer foams were made of aluminosilicate materials (fly ash) and foaming agents (H2O2 and Al powder), and the stabilizers were gypsum and portland cement. Additionally, surfactants were also used. It was found that better foaming effects were obtained for H2O2—it is a better foaming agent for geopolymers than Al powder. When using a hydraulic additive—a stabilizer in the form of cement—lower densities and better insulation parameters were obtained than when using gypsum. Portland cement is a better stabilizer than gypsum (calcium sulfates), although the effect may change due to the addition of surfactants, for example.

Improvement on Conductivity for Thick Film Aluminum Paste

With the development of thick-film paste, silver and copper are circulating in the market as the electric conductive fillings currently. Unfortunately, the cost of silver is exceedingly high, while the copper has to be sintered in the reducing atmosphere. In this study, we proposed to exert aluminum as the filling due to its low cost, good electrical conductivity, and capability of being sintered in air. By means of the fracture mechanism of the oxidation layer of the Al surface and the liquid phase sintering, the Al paste with high solid content is used to implement high electrical conductivity. Based on that Al powder with large particle size tends to fracture easily, while it is easy for Al powder with small size to fill the gap, we mixed Al powder with large and small particle sizes at different proportion, so that the internal micro-structure and the oxidization are observed. However, when glass frit was added into mixed Al powder, the Al particles are wet by glass frit for bonding Al particles as well as inhibiting oxidation. Effect of the glass frit content and the solid content of Al paste on conductivity are investigated in this study. The sheet resistance of Al paste sintered at 850 °C for 10 min. can be reduced to 4.5 mΩ/□ when Al paste is formulated based on the mixed Al particles with proportion of big to small (4:1) at 10 wt% glass frit content and 80 wt% solid content.