Aluminum–carbon nanotube (Al–CNT) composites represent a cutting-edge class of materials characterized by their exceptional mechanical, thermal, and electrical properties, making them highly promising for aerospace, automotive, electronics, and energy applications. This review systematically examines the impact of various fabrication methods, including conventional powder metallurgy, diffusion and reaction coupling, as well as adhesive and reaction bonding on the microstructure and performance of Al–CNT composites. The analysis emphasizes the critical role of CNT dispersion, interfacial bonding, and the formation of reinforcing phases, such as Al₄C₃ and Al₂O₃, in determining the mechanical strength, wear resistance, corrosion resistance, and thermal stability of these materials. The challenges of CNT agglomeration, high production costs, and difficulties in controlling interfacial interactions are highlighted alongside potential solutions, such as surface modifications and reinforcement strategies. The insights presented aim to guide future research and innovation in this rapidly evolving field.

Rocket engine nozzle blocks operate under extreme thermal and oxidative loads, requiring materials with high temperature resistance, dimensional stability, and a predictable lifetime without active cooling. This review provides a comparative overview of multimatrix composite materials-including C/C, C/SiC, SiC/SiC, MMC, and polymer-based ablative systems-representing the full spectrum of materials used in non-cooled rocket nozzles. The study highlights the evolutionary continuum from polymeric ablative systems to carbon, ceramic, and metallic matrices, demonstrating how each class extends operational limits in temperature capability, reusability, and structural integrity. Polymer and ablative composites serve as the foundation of thermal protection through controlled ablation and insulation, while carbon- and ceramic-based systems ensure long-term performance at ultra-high temperatures (>1600 °C). MMCs bridge these classes by combining strength, impact toughness, and thermal conductivity in transition zones. Particular attention is given to manufacturing technologies such as PIP, CVI, LPI, RS, powder metallurgy, casting, diffusion bonding, and filament winding, emphasizing their effect on microstructure, porosity, and lifetime. A practical selection matrix linking nozzle zones, mission profiles, and composite types is proposed, outlining trade-offs among performance, mass, lifetime, and manufacturability, and guiding the design of next-generation thermal protection and propulsion systems based on the multimatrix concept.

EPDM is widely used as the polymer matrix for solid rocket motor (SRM) internal thermal protection because of its low density, chemical inertness, and ability to form carbonaceous residue. Practical performance is frequently limited by weak char integrity and barrier properties, char oxidation, mechanical stripping in gas-dynamic flow, and by the poor comparability of published results due to non-uniform test conditions and reporting. This review systematizes studies on 0D nanofillers in EPDM ablatives and harmonizes the key metrics, including linear and mass ablation rates (LAR, MAR), back-face temperature (T_back), and solid residue yield. The major 0D additives-nSiO₂, nTiO₂, nZnO, and carbon black (CB) are compared, and their dominant mechanisms are summarized: degradation-layer structuring, reduced gas permeability, thermo-oxidative stabilization, and effects on vulcanization. Several studies report larger improvements for hybrid systems, where CB enhances char cohesion and retention, while oxide nanoparticles improve barrier performance and resistance to oxidation. Finally, an application-oriented selection matrix is proposed that accounts for thermal protection efficiency, processability, agglomeration limits, and density penalties to support EPDM coating design and improve comparability.

Elastomeric ablative coatings are essential for protecting solid rocket motor (SRM) combustion chambers from extreme thermal and erosive environments, and their performance is governed by both material composition and processing strategy. This review examines the main elastomer systems used for SRM insulation, including ethylene propylene diene monomer (EPDM), nitrile butadiene rubber (NBR), hydroxyl-terminated polybutadiene (HTPB), polyurethane (PU), silicone-based compounds, and related hybrids, and discusses how their rheological behavior, cure kinetics, thermal stability, and ablation mechanisms affect manufacturability and in-service performance. A comprehensive assessment of coating technologies is presented, covering casting, molding, centrifugal forming, spraying, automated deposition, and emerging additive-manufacturing approaches for complex geometries. Emphasis is placed on processing parameters that control adhesion to metallic substrates, layer uniformity, defect formation, and thermomechanical integrity under high-heat-flux exposure. The review integrates current knowledge on how material choice, surface preparation, and application sequence collectively determine insulation efficiency under operational SRM conditions. Practical aspects such as scalability, compatibility with complex chamber architectures, and integration with quality-control tools are highlighted. By comparing the capabilities and limitations of different materials and technologies, the study identifies key development trends and outlines remaining challenges for improving the durability, structural robustness, and ablation resistance of next-generation elastomeric coatings for SRMs.

This study investigates the impact of nickel doping on the thermal and combustion properties of ammonium perchlorate/carboxymethyl cellulose (AP/CMC) composites. Through comprehensive SEM-EDS, FTIR, XRD, DSC, TGA, and burning rate analyses, significant improvements in the structural and functional characteristics of the AP/CMC-Ni composite were observed compared to those of pure AP and AP/CMC composites. The SEM-EDS analysis revealed that nickel incorporation resulted in thicker and more irregular CMC fibers, indicating substantial morphological changes. The FTIR spectroscopy showed shifts in the O-H and C=O stretching bands, pointing to interactions between nickel ions and CMC functional groups. The XRD patterns highlighted a decrease in crystallinity and the presence of NiO phases, confirming the successful integration of nickel into the CMC matrix. The thermal analysis demonstrated that nickel doping significantly lowered the decomposition temperature of the AP/CMC composite, as evidenced by DSC, and enhances the thermal degradation process, as shown by TGA. The AP/CMC-Ni composite exhibited a higher burning rate across all of the tested pressures, highlighting the catalytic effect of nickel in improving the combustion efficiency. The burning rate for AP/CMC follows the power-law expression with constants a = 2.34 and n = 0.499, while for AP/CMC-Ni, the constants are a = 3.35 and n = 0.475. This study highlights the essential role of nickel doping in facilitating the decomposition of AP within the AP/CMC composite. By lowering the decomposition temperature, nickel enhances the overall combustion process, making the AP/CMC-Ni composite more efficient for applications requiring controlled thermal decomposition. These findings provide valuable insights for the design and development of high-performance composite materials in advanced industrial applications.