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Full-Text Articles in Mechanical Engineering

Production And Purification Of Zircon Opacifier From Zircon Found In The Coastal Area Of Bangladesh Aug 2008

Production And Purification Of Zircon Opacifier From Zircon Found In The Coastal Area Of Bangladesh

A.S. Md Abdul Haseeb

In this study the potentiality of Bangladesh zircon as a raw material for opacifier was examined. Preparation of zircon flour was done by both wet and dry ball milling. Wet milling of zircon was found to be much efficient than dry milling. Zircon flour of peak size 8 μm obtained by wet milling was purified by leaching in concentrated H2SO4 acid. Leaching time was varied from 2 to 20 h and sulphuric acid concentration ranged from 10 to 80 ml/l. Both un-purified and purified Bangladesh zircon flour were tested for their performance as opacifier in a couple of local ...


Friction And Wear Characteristics Of Electrodeposited Nanocrystalline Nickel-Tungsten Alloy Films Jan 2008

Friction And Wear Characteristics Of Electrodeposited Nanocrystalline Nickel-Tungsten Alloy Films

A.S. Md Abdul Haseeb

Electrodeposited nanocrystalline nickel-tungsten alloys are being investigated as an attractive alternative to electrodeposited nickel for applications involving fabrication of micro electro mechanical systems (MEMS). Ni-W alloys are also being considered as an environmentally friendly alternative to hard chrome plating in some cases. In applications involving sliding contacts such as in micro-gears in MEMS, mould inserts, etc., tribological properties of Ni-W alloys would be of relevance. In this work, the sliding friction and wear characteristics of Ni-W alloys with different tungsten contents were investigated and compared with that of nickel film deposited from sulphamate bath commonly used in microfabrication. For wear ...


Liga Fabrication Of Nanocrystalline Ni-W Alloy Micro Specimens From Ammonia-Citrate Bath Jan 2008

Liga Fabrication Of Nanocrystalline Ni-W Alloy Micro Specimens From Ammonia-Citrate Bath

A.S. Md Abdul Haseeb

Ammonia-citrate bath has been investigated for the deposition of nano crystalline Ni-W alloy micro components using the LIGA process. First the bath stability and deposit characteristics were studied. Fabrication of micro specimens were then carried out on silicon substrates covered with novolac as well as thick PMMA resist for LIGA. Effects of different parameters like current density, nickel ion and tungsten ion concentration in the bath, deposition time etc. on the deposit characteristics and current efficiency were studied. The deposited Ni-W samples were characterized by scanning electron microscopy, energy depressive X-ray spectroscopy, light optical microscopy and X-ray diffraction. Results show ...


Liga Fabrication Of Nanocrystalline Ni-W Alloy Micro Specimens From Ammonia-Citrate Bath Jan 2008

Liga Fabrication Of Nanocrystalline Ni-W Alloy Micro Specimens From Ammonia-Citrate Bath

A.S. Md Abdul Haseeb

Ammonia-citrate bath has been investigated for the deposition of nano crystalline Ni-W alloy micro components using the LIGA process. First the bath stability and deposit characteristics were studied. Fabrication of micro specimens were then carried out on silicon substrates covered with novolac as well as thick PMMA resist for LIGA. Effects of different parameters like current density, nickel ion and tungsten ion concentration in the bath, deposition time etc. on the deposit characteristics and current efficiency were studied. The deposited Ni-W samples were characterized by scanning electron microscopy, energy depressive X-ray spectroscopy, light optical microscopy and X-ray diffraction. Results show ...


Thermal Stability Of Electrodeposited Liga Ni-W Alloys For High Temperature Mems Applications Jan 2008

Thermal Stability Of Electrodeposited Liga Ni-W Alloys For High Temperature Mems Applications

A.S. Md Abdul Haseeb

For thermally stable LIGA materials for high temperature MEMS applications LIGA Ni-W layers and micro testing samples with different compositions (15 and 5 at% W) were electrodeposited. In order to investigate the thermal stability the Ni-W layers were annealed at different temperatures (300-700°C) and for different durations (1, 4, 16 h). Their microstructure and micro-hardness were than analysed after annealing and compared with those of as-deposited states. The observed microstructures show, in comparison to pure LIGA nickel, a small grain growth and a relatively stable structure up to 700°C. The micro-hardness values of the LIGA Ni-W layers are ...