Kamel Khimeche

Bio: Kamel Khimeche is an academic researcher from École Normale Supérieure. The author has contributed to research in topics: UNIFAC & UNIQUAC. The author has an hindex of 21, co-authored 73 publications receiving 1306 citations.

Physicochemical properties of microcrystalline nitrocellulose from Alfa grass fibres and its thermal stability

Abstract: The conventional cellulose nitrate (NC), used in many applications such as coating agent, main charge of propellant, museum artefacts, biofilter material, solid-phase immobilization supports for proteins, was mainly prepared from wood or cotton. The conventional NC presents many drawbacks such as low density, high friability and low combustion temperature. One approach to improve these shortcomings is the modification of the structure of the NC precursor (cellulose). In this work, microcrystalline cellulose nitrate was successfully produced from an inexpensive and easily renewable source which is Alfa grass. Fourier transform infrared spectroscopy indicates some modifications in the peak positions and intensities, suggesting that a significant difference between conventional and microcrystalline cellulose nitrate samples exists. According to X-ray diffraction results, microcrystalline cellulose nitrate samples were more crystalline than the conventional cellulose nitrate samples, where the increase of the crystallinity is 22 %. The morphology was investigated using scanning electron microscopy, showing a compact structure and a rough surface. In comparison with the commercial nitrocellulose material, the microcrystalline cellulose nitrate particles have good thermal stability, low viscosity, high nitrogen content and important quantity of gas released. Besides on these results, Alfa microcrystalline cellulose nitrate showed tremendous potential use as a propellant and gas generator component or other high value-added applications.

Solubility of diamines in supercritical carbon dioxide: Experimental determination and correlation

Abstract: In this work, the dynamic method is used for solubility measurements in supercritical carbon dioxide (Sc-CO 2 ) of some aromatic diamines (1,5-naphthalediamine, and 4,4′-diaminodiphenylmethane) and alkanediamines (1,10-decanediamine and 1,12-dodecanediamine), at pressures from 110 to 200 bar and temperatures from 313.15 to 333.15 K. Solubility in Sc-CO 2 cannot be reported for alkanediamines, since they interact with CO 2 . The experimental data for aromatic diamines were well correlated by Peng–Robinson equation of state (PR-EOS), and density-based models (Chrastil and Mendez-Santiago–Teja models). The partial molar volumes of the aromatic diamines in the supercritical fluid (SCF) phase were also estimated, according to the theory developed by Kumar and Johnston.

Study on the influence of ageing on thermal decomposition of double‐base propellants and prediction of their in‐use time

Abstract: A comparative study of the thermal decomposition of naturally and artificially aged double-base propellants has been carried out at five different heating rates in a dynamic nitrogen atmosphere using differential scanning calorimetry (DSC) technique. The results show that there is only one decomposition peak on DSC curves, and this decomposition has been accelerated by ageing. The influence of the heating rate on the DSC behaviour of the propellants was verified. The kinetic parameters such as activation energy and frequency factor and the thermodynamic parameters such as the enthalpy of activation, free energy of activation and critical explosion temperature for the compounds were obtained from DSC data using non-isothermal methods proposed by Kissinger and Ozawa. On the other hand, a prediction of the in-service period by van't Hoff's equation was performed and compared with the experimental results in order to check the constancy and validity of this method. As a result, the prediction procedure used to obtain the time–temperature profile was achieved with good accordance. Copyright © 2012 John Wiley & Sons, Ltd.

Recent progress in cellulose nanocrystals: sources and production

Abstract: Cellulose nanocrystals, a class of fascinating bio-based nanoscale materials, have received a tremendous amount of interest both in industry and academia owing to its unique structural features and impressive physicochemical properties such as biocompatibility, biodegradability, renewability, low density, adaptable surface chemistry, optical transparency, and improved mechanical properties. This nanomaterial is a promising candidate for applications in fields such as biomedical, pharmaceuticals, electronics, barrier films, nanocomposites, membranes, supercapacitors, etc. New resources, new extraction procedures, and new treatments are currently under development to satisfy the increasing demand of manufacturing new types of cellulose nanocrystals-based materials on an industrial scale. Therefore, this review addresses the recent progress in the production methodologies of cellulose nanocrystals, covering principal cellulose resources and the main processes used for its isolation. A critical and analytical examination of the shortcomings of various approaches employed so far is made. Additionally, structural organization of cellulose and nomenclature of cellulose nanomaterials have also been discussed for beginners in this field.

Nanocellulose: From Fundamentals to Advanced Applications

Abstract: Over the past few years, nanocellulose (NC), cellulose in the form of nanostructures, has been proved to be one of the most prominent green materials of modern times. NC materials have gained growing interests owing to their attractive and excellent characteristics such as abundance, high aspect ratio, better mechanical properties, renewability, and biocompatibility. The abundant hydroxyl functional groups allow a wide range of functionalizations via chemical reactions, leading to developing various materials with tunable features. In this review, recent advances in the preparation, modification, and emerging application of nanocellulose, especially cellulose nanocrystals (CNCs), are described and discussed based on the analysis of the latest investigations (particularly for the reports of the past 3 years). We start with a concise background of cellulose, its structural organization as well as the nomenclature of cellulose nanomaterials for beginners in this field. Then, different experimental procedures for the production of nanocelluloses, their properties, and functionalization approaches were elaborated. Furthermore, a number of recent and emerging uses of nanocellulose in nanocomposites, Pickering emulsifiers, wood adhesives, wastewater treatment, as well as in new evolving biomedical applications are presented. Finally, the challenges and opportunities of NC-based emerging materials are discussed.