A comprehensive review on processing, characteristics, and applications of cellulose nanofibrils/graphene hybrid-based nanocomposites: Toward a synergy between two-star nanomaterials.

Nanostructured materials are fascinating since they are promising for intensely enhancing materials' performance, and they can offer multifunctional features. Creating such high-performance nanocomposites via effective and mild approaches is an inevitable requirement for sustainable materials engineering. Nanocomposites, which combine two-star nanomaterials, namely, cellulose nanofibrils (CNFs) and graphene derivatives (GNMs), have recently revealed interesting physicochemical properties and excellent performance. Despite numerous studies on the production and application of such systems, there is still a lack of concise information on their practical uses. In this review, recent progress in the production, modification, properties, and emerging uses of CNFs/GNMs hybrid-based nanocomposites in various fields such as flexible energy harvesting and storage, sensors, adsorbents, packaging, and thermal management, among others, are comprehensively examined and described based on recent investigations. Nevertheless, numerous challenges and gaps need to be addressed to successfully introduce such nanomaterials in large-scale industrial applications. This review will certainly help readers understand the design approaches and potential applications of CNFs/GNMs hybrid-based nanocomposites for which new research directions in this emerging topic are discussed.

Unravelling the thermal behavior and kinetics of unsaturated polyester resin supplemented with organo-nanoclay.

The integration of nanoclays within polymeric systems to develop high-performance materials is an emerging research field that has garnered significant attention. In this context, an organically modified montmorillonite (OMMT) is utilized as a reinforcing agent for unsaturated polyester resin (UPR) with loads of 1%, 3%, and 5 wt%. The modification of montmorillonite nanoclay (MMT) using a quaternary ammonium compound is performed through an effective repetitive modification process under reflux conditions. The curing behavior of the unsaturated polyester resin containing organically modified clay catalyzed with methyl ethyl ketone peroxide (MEKP) initiator and promoted by cobalt naphthenate accelerator is investigated using dynamic differential scanning calorimetry (DSC) followed by kinetic analysis using isoconversional methods. The dynamic DSC curing curves showed a bimodal exothermic peak, where two independent reactions, namely, redox and thermal decomposition of the initiator occurred. In this study, novel insights into the curing reaction of the studied UPR and UPR/OMMT systems have been revealed through the application of the Trache-Abdelaziz-Siwani (TAS) and Sbirrazzuoli (VYA/CE) isoconversional methods. These methods have enabled the elucidation of the intricate mechanisms and phenomena that impact the curing reaction, including the dilution effect in the redox reaction and the diffusion phenomenon at the end of the thermal decomposition reaction. The incorporation of nanoclay into unsaturated polyester resin (UPR) resulted in a reduction in the activation energy for both the redox and thermal reactions. Specifically, the energetic barrier decreased from 93.85 and 101.58 kJ mol-1 for pristine UPR to 60.71 and 72.93 kJ mol-1 for UPR/OMMT-5 in the redox and thermal reactions, respectively. The addition of OMMT caused a significant decrease in the pre-exponential factor. The values of UPR/OMMT-5 were 2.75 × 105 and 5.50 × 106 for the redox and thermal decomposition reactions, respectively, compared to 1.41 × 1012 and 5.13 × 1013 for UPR. The thermogravimetric analysis demonstrated that UPR/OMMT systems were more stable than UPR.

Development and Characterization of New Energetic Composites Based on HNTO/AN Co-Crystal and Nitro-Cellulosic Materials.

To develop advanced cellulose-based energetic composites, new types of high-energy-density formulations containing hydrazine 3-nitro-1,2,4-triazol-5-one (HNTO)/ammonium nitrate (AN) cocrystals combined with nitrocellulose or nanostructured cellulose nitrate (NC and NMCC) were experimentally characterized. The prepared energetic formulations were analyzed in terms of their physicochemical properties, mechanical sensitivities, structural features, and thermal behavior. Their heats of combustion and theoretical energetic performance were assessed as well. Experimental results exhibited the inherent characteristics of the designed NC@HNTO/AN and NMCC@HNTO/AN, including improved density, specific impulse, and impact sensitivity compared to their raw compounds. Besides that, thermo-kinetic findings revealed that the as-prepared insensitive and high-energy-density composites undergo two exothermic decomposition processes, and that NC@HNTO/AN has higher thermal activity. The present study demonstrated the outstanding characteristics of the new composites and could serve as a reference for developing more advanced cellulose-based energetic formulations.

Posidonia oceanica (L.) Delile: A Mediterranean seagrass with potential applications but regularly and erroneously referred to as an algal species.

Posidonia oceanica (L.) Delile is one of the most abundant aquatic vascular higher plants in the Mediterranean Sea belonging to Posidoniaceas family. It is considered as a valuable natural source for multiple uses either for ecological functions or industrial applications. Nevertheless, this marine phanerogam is commonly confused with macroalgae, or seaweeds, known also as cryptogams. The present note intends to discuss the mis-use of the associated terminology of P. oceanica as algae in the scientific literature in order to avoid the widespread of this issue in the future. Thus, an extensive assessment of some important published woks has been conducted. This note will certainly allow the accurate nomenclature of this promising endemic species, which will continue its valorizations' ascension in several potential applications.

Towards Investigating the Effect of Ammonium Nitrate on the Characteristics and Thermal Decomposition Behavior of Energetic Double Base NC/DEGDN Composite.

This research work aimed to elaborate on a new modified double-base propellant containing nitrocellulose (NC), ammonium nitrate (AN), and diethylene glycol dinitrate (DEGDN). The developed AN/NC-DEGDN formulation was successfully obtained through a casting process and fully characterized in terms of its chemical structure, morphological features, and thermal behavior. Beforehand, theoretical calculation by the CEA-NASA program was applied to select the optimal composition of the formulation. Experimental findings demonstrated the homogenous dispersion of AN oxidizer in the NC-DEGDN matrix without alteration of their molecular structures. The catalytic influence of AN on the thermal decomposition behavior of NC-DEGDN film was also elucidated by thermal analyses. When AN was incorporated into the formulation, the decomposition peak temperatures for the different decomposition processes were shifted toward lower temperatures, while the total enthalpy of decomposition increased by around 1272.24 J/g. In addition, the kinetics of the thermal decomposition of the developed modified double base propellant were investigated using DSC results coupled with model kinetic approaches. It was found that the addition of AN decreases the activation energy of nitrate esters from 134.5 kJ/mol to 118.84 kJ/mol, providing evidence for its excellent catalytic effect. Overall, this investigation could serve as a reference for developing future generation of modified double-base propellants.

Elaboration, Characterization and Thermal Decomposition Kinetics of New Nanoenergetic Composite Based on Hydrazine 3-Nitro-1,2,4-triazol-5-one and Nanostructured Cellulose Nitrate.

This research aims to develop new high-energy dense ordinary- and nano-energetic composites based on hydrazine 3-nitro-1,2,4-triazol-5-one (HNTO) and nitrated cellulose and nanostructured nitrocellulose (NC and NMCC). The elaborated energetic formulations (HNTO/NC and HNTO/NMCC) were fully characterized in terms of their chemical compatibility, morphology, thermal stability, and energetic performance. The experimental findings implied that the designed HNTO/NC and HNTO/NMCC formulations have good compatibilities with attractive characteristics such as density greater than 1.780 g/cm3 and impact sensitivity around 6 J. Furthermore, theoretical performance calculations (EXPLO5 V6.04) displayed that the optimal composition of the as-prepared energetic composites yielded excellent specific impulses and detonation velocities, which increased from 205.7 s and 7908 m/s for HNTO/NC to 209.6 s and 8064 m/s for HNTO/NMCC. Moreover, deep insight on the multi-step kinetic behaviors of the as-prepared formulations was provided based on the measured DSC data combined with isoconversional kinetic methods. It is revealed that both energetic composites undergo three consecutive exothermic events with satisfactory activation energies in the range of 139-166 kJ/mol for HNTO/NC and 119-134 kJ/mol for HNTO/NMCC. Overall, this research displayed that the new developed nanoenergetic composite based on nitrated cellulose nanostructure could serve as a promising candidate for practical applications in solid rocket propellants and composite explosives.

Cellulose nanofibrils-graphene hybrids: recent advances in fabrication, properties, and applications.

With the fast-developing social economy and the acceleration of industrialization, seeking effective renewable, sustainable, and environmentally friendly resources that show promising properties is an urgent task and a crucial means to achieve sustainable progress in the face of the growing depletion of non-renewable resources and the deterioration of environmental issues. Cellulose nanofibrils (CNFs) are natural polymeric nanomaterials with excellent biocompatibility, biodegradability, good mechanical features, high strength, low density, high specific surface area, and tunable chemistry. Their combination with other nanomaterials, such as graphene derivatives (GNMs), has been demonstrated to be effective since they produce hybrids with outstanding physicochemical properties, tailorable functionality, and high performance. In this review, recent advances in the preparation, modification, and emerging application of CNFs/GNMs hybrids are described and discussed using the latest studies. First, the concise background of nanocellulose and graphene derivatives is provided, followed by the interfacial interactions between CNFs and GNMs. The different hybrids exhibit great promise in separation, adsorption, optics, flexible electronics, energy storage, thermal management, barrier and packaging, and electromagnetic shielding. The main challenges that inhibit the applicability of these hybrids are finally highlighted, and some perspectives for future research directions are provided.

Effect of silane modified microcrystalline cellulose on the curing kinetics, thermo-mechanical properties and thermal degradation of benzoxazine resin.

In the frame of developing sustainable, eco-friendly and high performance materials, microcrystalline cellulose modified through silane coupling agent (MCC Si) is used as a reinforcing agent of benzoxazine resin to manufacture composites at different loadings of 5, 10, 15, 20 wt%. The structural, morphological and crystallinity characterizations of the modified MCC were initially performed to scrutinize the changes and confirm the modification. Then, an investigation on the crosslinking process of the prepared composites was held through curing kinetic study employing isoconversional methods. The kinetic data revealed a decrease in the average values of activation energy and the pre-exponential factor, particularly for composite supplemented with 10% MCC Si, whereas all samples disclosed a tendency of an autocatalytic curing mechanism. Furthermore, the study of the dynamic mechanical properties and degradation features of the cured specimens, respectively, indicated a superior stiffness attributable to the good interaction between BA-a and MCC Si, and enhanced thermal stability for the composites compared to pristine resin.

Optimized energetic HNTO/AN co-crystal and its thermal decomposition kinetics in the presence of energetic coordination nanomaterials based on functionalized graphene oxide and cobalt.

The present research aims to select the optimal molar ratio of hydrazine 3-nitro-1,2,4-triazol-5-one (HNTO) and ammonium nitrate (AN) to produce an energetic co-crystal. For a comparison purpose, the heat release, cost, density and hygroscopicity of the different co-crystals were evaluated. The obtained results indicated that HNTO/AN at the 1 : 3 ratio exhibited a higher heat release, better thermal stability, low water content and a reasonable cost, compared to other co-crystals. This new co-crystal was fully characterized through powder X-ray diffraction (XRD), infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), confirming that this latter displayed similar characteristics to those of the co-crystal with a 1 : 1 ratio, which was recently developed. On the other hand, the catalytic activity of two energetic coordination polymers of triaminoguanidine-cobalt (T-Co) complexes, with or without graphene oxide (GO-T-Co-T), on the thermolysis of the developed co-crystal has been also assessed by DSC under non-isothermal conditions. It is revealed that these catalysts have greatly decreased the decomposition temperature of the HNTO/AN cocrystal. Moreover, because of the complete decomposition in the case of the (HNTO/AN)/GO-T-Co-T composite, the heat release has been increased as well. Isoconversional integral kinetic methods were exploited to determine the kinetic parameters of the different systems. According to the obtained results, these catalysts have a strong catalytic action on the decomposition of the co-crystal AN/HNTO for which the activation energy and the pre-exponential factor are considerably lowered. Consequently, the developed co-crystal and the energetic catalysts could be considered as potential ingredients for the next generation of composite solid propellant formulations.

A promising energetic biopolymer based on azide-functionalized microcrystalline cellulose: Synthesis and characterization.

In the current investigation, azidodeoxy-microcrystalline cellulose nitrate (AMCCN) as a novel promising nitrogen-rich energetic biopolymer was synthesized, and its features were compared to those of azidodeoxy-pristine cellulose nitrate (APCN), conventional cellulose nitrate (PCN) and microcrystalline cellulose nitrate (MCCN). The produced nitrated samples and their precursors were fully characterized using various analytical techniques. In addition, the heats of combustion and mechanical sensitivities of all nitrated biopolymers were evaluated, and their energetic performances were predicted by EXPLO5 V6.04 software. The obtained results provide evidence for the effectiveness of the applied chemical functionalization approach to synthesize the relatively insensitive AMCCN and APCN with nitrogen content of 22.75 % and 22.50 %, density of 1.718 g/cm3 and 1.706 g/cm3, and detonation velocity of 7707 m/s and 7533 m/s, respectively, which are higher than those of PCN. This work opens avenues to design promising energetic biopolymers based on renewable microcrystalline cellulose for potential application in advanced high performance solid propellants and explosives.

Characterization of raw and treated Arundo donax L. cellulosic fibers and their effect on the curing kinetics of bisphenol A-based benzoxazine.

In the present work, giant reed cellulosic fibers (Arundo donax L., RF) were explored as reinforcement of bisphenol A-based benzoxazine (BA-a). RF were extracted from giant reed cane, and subjected to different chemical treatments using either alkaline, silane or their combining treatments. The examination of the structural, thermal, crystallinity and morphological properties of the untreated (NRF) and treated fibers (TRF) was carried out using different analytical techniques. Broadly, the morphology of the treated fibers is affected, their crystallinity and thermal stability increased. The investigation of the effect of the treated fibers on the curing kinetics of composites based on BA-a was performed by differential scanning calorimetry (DSC) technique, under non-isothermal conditions, and isoconversional integral kinetic methods. A decrease in the heat of curing as well as activation energy (Ea) was reported. The Avrami-Erofeev autocatalytic kinetic model was the most appropriate to describe the curing reactions and the predicted curves from the calculated kinetic parameters fitted well with experimental data.

Organosolv lignins as new stabilizers for cellulose nitrate: Thermal behavior and stability assessment.

Cellulose nitrate, commonly known as nitrocellulose (NC), and its corresponding propellants naturally decompose at normal conditions. To avoid early degradation, unexpected explosion, energy loss, and ensure a safe storage, stabilizing agents are often introduced within its compositions. Conventional stabilizers, such as aromatic amines like diphenylamine (DPA) and urea, can produce carcinogenic/toxic substances during propellants shelf life. Thus, a need for alternative stabilizing agents, which offer similar/better effectiveness and display a non/low toxicity, remains a challenge. This paper investigates the stabilizing effect of two organosolv lignins (OL), obtained from Aleppo pine (AP) and Eucalyptus globulus (EG), on NC. For this purpose, conventional stability tests and kinetic modeling are applied for different samples (S1-S4) using 3% of stabilizer, which are S1, pure NC; S2, NC + DPA; S3, NC + OL(AP); and S4, NC + OL(EG). Beforehand, FTIR spectroscopy and DSC analysis have been used to check the compatibility of these potential stabilizers and NC. The obtained results via Bergmann-Jung and vacuum stability tests suggested that the prepared mixtures are stable. The kinetic study based on DSC data using isoconversional methods shows that both stabilizers display a good stabilizing effect. The reactivity between the different organosolv lignins and NOx released during the degradation of NC has been well highlighted using FTIR and TGA analyses. Hence, these efficient, environmentally friendly and readily available substances can be effectively used as stabilizers for NC-based formulations.

Nanocellulose: From Fundamentals to Advanced Applications.

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.

Microcrystalline cellulose from Posidonia oceanica brown algae: Extraction and characterization.

Posidonia oceanica brown algae (POBA) represent an abundant and renewable biomass in Algerian seas. In the present study, the POBA were chemically treated through delignification and alkali treatment followed by acid hydrolysis to produce pure microcrystalline cellulose (MCC). FTIR analysis indicates that most lignin and hemicellulose were eliminated during the chemical treatments. The XRD measurements revealed that the obtained cellulose and MCC belong to cellulose I polymorph, with crystallinity index of 60.50% and 74.23%, respectively. SEM micrographs of the produced MCC showed a non-uniform micro sized rod-like shape morphology with an average diameter of 8.4 ±â€¯2.1 µm. The thermal analysis results exhibited that the decomposition temperature of the prepared MCC shifted to higher temperature compared to that of the respective cellulose and raw POBA. The authenticity of the prepared MCC was also examined by comparing its physicochemical properties with those of commercial MCC. Based on these analyses, POBA-MCC showed tremendous potential to be used in several applications.

Analytical Methods for Stability Assessment of Nitrate Esters-Based Propellants.

Nitrate esters-based propellant (NEBP) belongs to the main classes of energetic materials being used in civilian and military applications. These NEBPs are not highly stable, and during aging, some of their functional characteristics may change, what can lead to serious safety problems. A thorough analytical characterization of NEBP is of fundamental importance to provide an adequate support for their stability and safe life assessment. Moreover, in order to safely store and fully exploit these energetic materials, accurate analytical techniques and strategies are indispensable to efficiently judge their properties during aging. Although various methodologies have been developed worldwide to evaluate the aging behavior of NEBP, the characterization is not a simple task and often involves the combination of several techniques, whose results have to be evaluated together. This review sought to evaluate existing analytical techniques which can be utilized for a suitable analysis of NEBP stability and aging, evidencing their respective advantages and shortcomings. The employment of each examined technique is described and discussed by relevant examples from the literature.