Development of a novel micro-spray-assembly process for multilayer ultra-thin film formation

A novel micro-spray-assembly process and an automatic device to fabricate multilayer ultra-thin film are introduced. Employing self-assembly monolayer (SAM) technique, ultra-thin film can be assembled by utilizing the micro-spray-assembly device. The thickness and roughness of each monolayer can be controlled by varying various materials attributes, i.e., deposition time, ionic strength, pH value, molecular concentration and by selecting different manufacturing parameters of the automatic device such as spraying rate, size of micro-drop, N₂ flow rate, temperature of N₂ flow.

Fabrication of carbon nanofiber by pyrolysis of freeze-dried cellulose nanofiber

The possibility of fabricating carbon nanofibers from cellulose nanofibers was investigated. Cellulose nanofiber of ~50 nm in diameter was produced using ball milling in an eco-friendly manner. The effect of the drying techniques of cellulose nanofibers on the morphology of carbon residue was studied. After pyrolysis of freeze-dried cellulose nanofibers below 600 °C, amorphous carbon fibers of ~20 nm in diameter were obtained. The pyrolysis of oven-dried precursors resulted in the loss of original fibrous structures. The different results arising from the two drying techniques are attributed to the difference in the spatial distance between cellulose nanofiber precursors.

Preparation and characterization of graphitic carbon nitride through pyrolysis of melamine

Graphitic carbon nitride (g-C₃N₄) has been synthesized via a two-step pyrolysis of melamine (C₃H₆N₆) at 800°C for 2 h under vacuum conditions. X-ray diffraction (XRD) patterns strongly indicate that the synthesized sample is g-C₃N₄. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) morphologies indicate that the product is mainly composed of graphitic carbon nitride. The stoichiometric ratio of C:N is determined to be 0.72 by elemental analysis (EA). Chemical bonding of the sample has been investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Electron energy loss spectroscopy (EELS) verifies the bonding state between carbon and nitrogen atoms. Optical properties of the g-C₃N₄ were investigated by PL (photoluminescence) measurements and UV–Vis (ultraviolet–visible) absorption spectra. We suppose its luminescent properties may have potential application as component of optical nanoscale devices. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were also performed.

A study of pyrolysis conditions on carbon nanofiber properties produced from freeze-dried cellulose nanofibers

In the present work, carbon nanofibers were prepared by pyrolysis of freeze-dried cellulose nanofiber and the effect of pyrolysis conditions on the properties of carbon nanofiber was studied. SEM analysis revealed that slow heating rates below 400oC are critical to maintain the fibrous morphology after carbonization. The present study demonstrated the possibility of producing carbon nanofibers of ≤ 30 nm in diameter by a simple and scalable method.

Pyrolysis of municipal green waste: a modelling, simulation and experimental analysis

Pyrolysis is the thermo-chemical conversion of carbonaceous feedstock in the absence of oxygen to produce bio-fuel (bio-oil, bio-char and syn-gas). Bio-fuel production from municipal green waste (MGW) through the pyrolysis process has attracted considerable attention recently in the renewable energy sector because it can reduce greenhouse gas emissions and contribute to energy security. This study analyses properties of MGW feedstock available in Rockhampton city of Central Queensland, Australia, and presents an experimental investigation of producing bio-fuel from that MGW through the pyrolysis process using a short sealed rotary furnace. It was found from the experiment that about 19.97% bio-oil, 40.83% bio-char and 29.77% syn-gas can be produced from the MGW. Then, a four-stage steady state simulation model is developed for pyrolysis process performance simulation using Aspen Plus software. In the first stage, the moisture content of the MGW feed is reduced. In the second stage, the MGW is decomposed according to its elemental constituents. In the third stage, condensate material is separated and, finally, the pyrolysis reactions are modelled using the Gibbs free energy minimisation approach. The MGW's ultimate and proximate analysis data were used in the Aspen Plus simulation as input parameters. The model is validated with experimentally measured data. A good agreement between simulation and experimental results was found. More specifically, the variation of modelling and experimental elemental compositions of the MGW was found to be 7.3% for carbon, 15.82% for hydrogen, 7.04% for nitrogen and 5.56% for sulphur. The validated model is used to optimise the biofuel production from the MGW as a function of operating variables such as temperature, moisture content, particle size and process heat air-fuel ratio. The modelling and optimisation results are presented, analysed and discussed.

Survival, oxidative stability, and surface characteristics of spray dried co-microcapsules containing omega-3 fatty acids and probiotic bacteria

The objective of the study was to determine optimum inlet and outlet air temperatures of spray process for producing co-microcapsules containing omega-3 rich tuna oil and probiotic bacteria L. casei. These co-microcapsules were produced using whey protein isolate and gum Arabic complex coacervates as shell materials. Improved bacterial viability and oxidative stability of omega-3 oil were used as two main criteria of this study. Three sets of inlet (130°C, 150°C, and 170°C) and outlet (55°C, 65°C, and 75°C) air temperatures were used in nine combinations to produce powdered co-microcapsule. The viability of L. casei, oxidative stability of omega-3 oil, surface oil, oil microencapsulation efficiency, moisture content, surface elemental composition and morphology of the powdered samples were measured. There is no statistical difference in oxidative stability at two lower inlet air temperatures (130°C and 150°C). However, there was a significant decrease in oxidative stability when higher inlet temperature (170°C) was used. The viability of L. casei decreased with the increase in the inlet and outlet air temperatures. There was no difference in the surface elemental compositions and surface morphology of powdered co-microcapsules produced under these nine inlet/outlet temperature combinations. Of the range of conditions tested the co-microcapsules produced at inlet-outlet temperature 130–65°C showed the highest bacterial viability and oxidative stability of omega-3 and having the moisture content of 4.93 ± 0.05% (w/w). This research shows that powdered co-microcapsules of probiotic bacteria and omega-3 fatty acids with high survival of the former and high stability against oxidation can be produced through spray drying.