Search

Miniaturization of chemical system has attracted tremendous interests in chemistry and biology due to many advantages such as enhancement in heat/mass transfer rates, reduction in expensive reagents and hazardous wastes, and facilitation of massive parallelization in reaction/catalyst screening and optimization Fabrication of microchemical systems (μCSs) has matured around materials such as silicon, glass and polymers, which are not particularly suitable for harsh environment such as high pressure, high temperature, and corrosive reactants. The main objective of this paper is to introduce a new ceramic-based fabrication framework for such harsh environment. This paper demonstrates the feasibility of the new technique by constructing a micro-burner, which can be used as on-chip heater or sensor. The proposed technique overcomes one major roadblock in fabrication of ceramic-based μCSs. The unreliable joining and assembling of simple ceramic components are eliminated by utilizing a fugitive phase machined into an intricate shape of an internal combustion chamber and channels. The main fabrication strategy is to use the advantage of powder, offering the fluidity to flow into a complex cavity or around the solid phase as well as the rigidity to remove the undesirable sections. The paper demonstrates the unique method of fabricating a micro-burner that can sustain an oxy-hydrogen flame for an extensive period and under cyclic operations.

Ceramic-based microchemical systems (μCSs) are more suitable for operation under harsh environments such as high temperature and corrosive reactants compared to the more conventional μCS materials such as silicon and polymers. With the recent renewed interests in chemical manufacturing and process intensification, simple, inexpensive, and reliable ceramic manufacturing technologies are needed. The main objective of this paper is to introduce a new powder-based fabrication framework, which is a one-pot, cost-effective, and versatile process for ceramic μCS components. The proposed approach employs the compaction of metal-oxide sub-micron powders with a graphite fugitive phase that is burned out to create internal cavities and microchannels before full sintering. Pure alumina powder has been used without any binder phase, enabling more precise dimensional control and less structure shrinkage upon sintering. The key process steps such as powder compaction, graphite burnout during partial sintering, machining in a conventional machine tool, and final densification have been studied to characterize the process. This near-full density ceramic structure with the combustion chamber and various internal channels was fabricated to be used as a micro-burner for gas sensing applications.

A general method was proposed to classify fuel efficiency of agricultural tractors using fuel consumption data taken from the OECD tractor test report. The classification index comprised of four sub-indexes was designed to reflect operational characteristics of tractors and manufacturer’s fuel saving technology embedded in tractors. It was also intended to have tractors distributed normally over the classification grades. The weightings for the sub-indexes, number of classification grades and updating period of the index value were also discussed. The proposed method was applied to classify fuel efficiency of tractors in Korea into a five-grade system with 15% for the 1st, 20% for the 2nd, 30% for the 3rd, 20% for the 4th, and 15% for the 5th grades, respectively. The index values for each grade were calculated on the basis of performance data of 131 tractors tested over the five-year period from 2006 to 2010 and given as a function of rated PTO power. The classification results showed a reasonable distribution of tractors over the grades as intended. The proposed method can be utilized flexibly by assigning proper weightings to the sub-indexes depending on the classification purpose.