The Effect of Particle Shell on Cooling Rates in Oil-in-Oil Magnetic Pickering Emulsions

Pickering emulsions (particle-stabilized emulsions) are usually considered because of their unique properties compared to surfactant-stabilized emulsions including better stability against emulsion aging. However, the interesting feature of particle-stabilized emulsions could be revealed during their magnetic heating. When magnetic particles constitute a shell around droplets and the sample is placed in an alternating magnetic field, a temperature increase appears due to energy dissipation from magnetic relaxation and hysteresis within magnetic particles. We hypothesize that the solidity of the magnetic particle shell around droplets can influence the process of heat transfer from inside the droplet to the surrounding medium. In this way, particle-stabilized emulsions can be considered as materials with changeable heat transfer. We investigated macroscopically heating and cooling of oil-in-oil magnetic Pickering emulsions with merely packed particle layers and these with a stable particle shell. The change in stability of the shell was obtained here by using the coalescence of droplets under the electric field. The results from calorimetric measurements show that the presence of a stable particle shell caused a slower temperature decrease in samples, especially for lower intensities of the magnetic field. The retarded heat transfer from magnetic Pickering droplets can be utilized in further potential applications where delayed heat transfer is desirable.

Studi penggunaan membran berslot untuk memproduksi emulsi minyak/air

Emulsion is dispersion system, which consist of two or more immiscible liquids. If this system is not stable, particle dispersed will form separate layer. The degree of instability will be greater if size of dispersed particles is not uniform. Generally, emulsion is produced by using high speed homogenizer, which will destruct the product. Some technology has been developed to overcome this problem. One of such technology is membrane emulsification, where the emulsion is flowed through the membrane so the size of particles will be smaller and more uniform. Symmetric membrane, which is used effectively to produce emulsion, has been used in this research. From the experiments, it has been proved that 28 microns membrane could produce emulsion, which has small and uniform size of particles. Emulsion with feed concentration of 10 % w/w and concentration of surfactant 3 % w/w has the highest degree of stability with particle sizes in the range of 3.5–13.5 microns. Fluxes were decreased if we use higher feed and surfactant concentration.Keywords: Emulsion, microfiltration, slotted membraneAbstrakEmulsi adalah dispersi dua atau lebih cairan yang tidak bercampur. Jika sistem ini tidak stabil, maka partikel terdispersi akan bergabung membentuk lapisan terpisah. Ketidakstabilan emulsi semakin tinggi jika ukuran partikel terdispersi besar dan distribusi ukurannya tidak seragam. Umumnya pembuatan emulsi dilakukan dengan pengadukan kecepatan tinggi yang merugikan jika bahan sensitif terhadap tekanan. Banyak cara dikembangkan untuk mengatasi hal ini, salah satunya adalah teknologi membran emulsifikasi, dimana emulsi dilewatkan melalui membran agar ukuran partikel terdispersi menjadi lebih kecil dan seragam sehingga emulsi stabil. Membran simetris yang efektif untuk memproduksi emulsi adalah membran mikrofiltrasi berslot seperti dalam penelitian ini. Hasil percobaan menunjukkan bahwa penggunaan membran berslot 28 m memberikan ukuran dan distribusi partikel yang kecil dan seragam. Emulsi minyak dalam air yang paling stabil adalah pada konsentrasi umpan 10% (b/b) dan konsentrasi surfaktan 3% (b/b) dengan ukuran partikel berkisar antara 3,5–13,5 µm. Fluks menurun bila konsentrasi umpan dan surfaktan semakin besar.Kata kunci: emulsi, mikrofiltrasi, membran berslot

Efficient formation of oil-in-oil Pickering emulsions with narrow size distributions by using electric fields

We propose a new bulk approach to fabricating Pickering emulsions. We used electric fields not only to facilitate coalescence but also to manipulate surface particles and to induce droplet rotation, each contributed to formation of stable particle-covered droplets.

Synthesis of calcium carbonate in trace water environments

Calcium carbonate (CaCO3) was synthesized from diverse water-free alcohol solutions, resulting in the formation of vaterite and calcite precipitates, or stable particle suspensions, with the dimensions and morphology depending upon the conditions used.