Guide for stability evaluation of ammonium nitrate-based emulsions

Funaki, Amanda Rie; Lenzi, Marcelo Kaminski; Santos, Alexandre Ferreira

doi:10.1590/0370-44672023760008

Brasil

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Mining • REM, Int. Eng. J. 76 (4) • Oct-Dec 2023 • https://doi.org/10.1590/0370-44672023760008 linkcopy

Guide for stability evaluation of ammonium nitrate-based emulsions

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This article aims to compilate stability measurement tests for explosive emulsions (EE), which were developed and used in the last decades. So, it could serve as a stability guide for EEs. The main methodologies to evaluate the condition of the emulsion’s matrix is through microscopy, DLS, viscosity, and rheology, which can preview the stability of a freshly manufactured emulsion within maximum 30 days, since it can undergo physically (centrifugation, compression, and direct contact with water). Thermal tests for (freeze-thaw) can also be performed.

Keywords: explosive emulsion; stability; ammonium nitrate; crystallization

Equipment	Methodology	Reference
Olympus IX 81 combined with FV-500	A drop of emulsion was poured over a glass slide. Then, a cover slip was posed, and a drop of immersion oil was poured.	Sharu et al., 2017
Optical Microscope Bioptika	The emulsion was diluted in mineral oil and one drop of this mixture was poured over a glass slide. Over it, a cover slide was positioned, and one drop of immersion oil was poured. The image was captured with a 100x-zoom lens.	Funaki, 2020

Equipment	Methodology	Reference
LA-500 (Horiba)	Dilution of hot emulsion in paraffinic oil until it acquires fluidic consistency, so it can flow. Then, a drop of the mixture is poured in hexane under agitation and circulation in a quartz cell, until it reaches an adequate transmittance	Das et al., 1992
Mastersizer-2000 (Malvern Instruments)	Dispersion of emulsion in oil to obtain a diluted solution to avoid the agglomeration of the droplets	Kovalchuk et al., 2012

Microscope	Evaluation	Sample preparation	Methodology	Reference
Nikon DS-Fi1 optical microscopy	Microstructure	-	-	Zhang et al., 2017
Leica optical microscope	Crystal formation	-	Use of 500x-zoom lens with unpolarized and crossed polarized together	Al-Sabagh et al., 2017
Cryo-FEG-SEM	Microstructure	The emulsion was frozen with liquid nitrogen at -190 °C. Then, it was fragmented and sublimated at -90°C for 5 minutes. Finally, the samples were covered with platinum at 10 mA for 30 s.	Resulting image was obtained with acceleration voltage of 5 kV	Sharu et al., 2017
Metallographic microscope	Crystal formation	-	Use of 10x-zoom lens	Funaki, 2020

Rheometer	Sample preparation	Methodology	Reference
MCR 101 (Anton Paar) with PP50 flat	Gap of 1 mm 25°C	Amplitude sweep test: strais from 0.1% to 200% at frequency of 1Hz.	Alilovic et al., 2005
MCR300 (Paar Physica)	Bob-in-cup and cylinder-in-cylinder measuring units with a sandblasted bob surface	Stress: stress from 1 to 300 Pa with duration of 200 s. Steady shear rate measurement: flow curves from 1.10⁻⁴ to 1.10³ s⁻¹. Dynamic measurements: amplitude sweep regime with different frequencies and/or a frequency sweep regime at small amplitudes of deformations (stresses)	Masalova et al., 2013
Gemini HR Nano200	25°C in stationary mode, coneplate and a PP20 flat	Amplitude sweep test: strains from 0,05% to 50% at a frequency of 1 Hz. Temperature of 25°C. Steady shear rate measurement: 10 – 0.00015 s⁻¹ Stress: from 50 to 500 Pa at 25°C and 1 Hz Temperature variation: Under 100 Pa external force and 1 Hz, a sample is manteined at temperature from 25 to 80°C during 1200 s, then kept at 80°C for 100 s and finally at temperatures from 80 to 25°C for 1200 s.	Wang et al., 2013
Rotational stress rheometer MCR 502 (Paar Physica)	Sandblasted plate-plate geometry with 50 mm diameter and 1 mm gap	Amplitude sweep test: strains from 0.01% to 200% at a frequency of 1 Hz. Temperature of 30°C. Steady shear measurement: flow curves from 10⁻⁴ to 10² s⁻¹. Temperature of 85°C.	Al-Sabagh et al., 2017
Physica MCR 501 (Paar Physica)	25 °C, parallel plates (diameter of 25 mm) spaced 1 mm	Amplitude sweep test: strains from 0.1% to 200% at a frequency of 1 Hz. Frequency sweep test: range of frequencies of 0.01 to 300 rad/s at 0.1% strain. Steady shear rate measurement: flow curves from 0.001 to 30 s⁻¹.	Haru et al., 2017

Rotation	Cycles	Evaluation	Reference
3.600 rpm	2 × 15 min	Mean droplet size before and after the procedure	Funaki, 2020

Freezing temperature/ time	Temperature of thawing/ time	Method of freezing	Method of thawing	Cycles	Evaluation	Reference
−18°C/22h	40°C/2h	Freezer	Water	0 – 3	Droplet size and physical stability	Xu et al., 2016
−10°C/16h	50°C/8h	Test chamber with high and low temperature		40	Emulsion mass	Wang et al., 2017
−20°C/12h	65°C/12h	Dynamic climatic chamber (Binder)		14	Viscosity, droplet size and microstructure	Funaki, 2020

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Acessibilidade / Reportar erro

[TFN1] Before the analysis through a software, it is necessary to set calibration scale with a calibration slide that is to know the correspondent distance (μm) in a pixel.