Phase Decomposition Research Articles

Reactions of La1-xNdxSrCoO4 Ruddlesden-Popper phases under reducing atmospheres

The reactions and behavior of La1-xNdxSrCoO4 Ruddlesden-Popper phases were investigated under vacuum and hydrogen atmospheres with varying Nd content (x = 0, 0.25, 0.5, 0.75, 1) and temperatures ranging from 250 to 720°C. Under vacuum (total pressure between 4 and 5 ×10-3 mbar, pO2 = 10-3 mbar), linear thermal expansion is observed up to around 450°C, followed by continuous formation of La1-xNdxSrCoO4-δ phases up to about 700°C, where decomposition into individual oxides (La2O3, Nd2O3, SrO) and Co occurs. La1-xNdxSrCoO4-δ formation starts at lower temperatures with increasing Nd content, and contrary to LaSrCoO4, with addition of Nd, La1-xNdxSrCoO4-δ formation completes before phase decomposition occurs. Under hydrogen atmosphere (5%H2-95%Ar), the reduction reaction La1-xNdxSrCoO4 + δ H2(g) = La1-xNdxSrCoO4-δ + δ H2O(g) initiates at about 300°C and completes around 400°C, yielding the La1-xNdxSrCoO3.5 phase, with higher reactivity observed for x = 0.5 among different Nd contents.

Investigation on Enhancement of AP/HTPB/Al Composite Solid Propellant Combustion Characteristics via DC Electric Field

ABSTRACT To investigate the influence mechanisms of DC electric fields on the combustion of solid propellants, a numerical model for the combustion characteristics of AP/HTPB/Al composite solid propellant under the DC electric field is established. Effects of the applied electric field on combustion flame structure, combustion surface temperature distribution, and mixing fraction distribution are analyzed. The results indicate that the applied electric field enhances the mixing effect of the propellant gas phase decomposition products, thereby altering the flame structure and bringing it closer to the combustion surface. The application of the electric field leads to an increase in the combustion surface temperature by 20–70 K. The effect of the negative electric field on the combustion surface temperature and burning rate is more significant compared to that of the positive electric field. The results provide valuable theoretical guidance in the field of solid engine combustion control.

Pre-deformation assisted fabrication of bulk Nd2Fe14B/α-Fe nanocomposites with high energy density

For Nd2Fe14B/α-Fe nanocomposite magnets, which exhibit great superiority in theoretical energy products, it is a great challenge to obtain controlled nano-scale microstructural features while eliminating the harmful metastable phases due to the general metastable fabrication methods. Here, we report a strategy to control the nano-scale features and simultaneously eliminate metastable phases for Nd2Fe14B/α-Fe nanocomposites through low-temperature pre-deformation of amorphous alloys combined with subsequent thermal annealing. The resultant bulk Nd2Fe14B/α-Fe nanostructure exhibits desired ultrafine grain sizes, ∼20 nm for soft-magnetic α-Fe phase with a high fraction of Vα-Fe ≈ 30 wt% and ∼33 nm for hard-magnetic Nd2Fe14B phase. The desired microstructure results in a larger coercivity (Hci = 4.1 kOe) and higher saturation magnetization (Ms = 1.51 T) compared to those (Hci = 3.3 kOe and Ms = 1.35 T) of the counterpart without pre-deformation, contributing to a high energy density of 26.3 MGOe. This energy density is 200% larger than that of the counterpart without pre-deformation and far beyond that (around 20 MGOe) of previously reported bulk Nd2Fe14B/α-Fe nanocomposites with Vα-Fe ≥ 20 wt%. The superior property stems from the purposely introduced low-temperature pre-deformation that changed the structure and local chemistry of the amorphous alloy, facilitating the decomposition of harmful metastable phases and the formation of Nd2Fe14B phase during annealing processes, which lowers the temperature, from 750 to 700 °C for producing the Nd2Fe14B/α-Fe nanostructure and thus yields ultrafine nanograins. These results demonstrate an effective means to prepare high-performance bulk Nd2Fe14B/α-Fe nanocomposite magnets.

Microstructure and Mechanical Properties of the Powder Metallurgy Nb-16Si-24Ti-2Al-2Cr Alloy.

The Nb-16Si-24Ti-2Al-2Cr alloy was prepared by plasma rotating electrode process (PREP) technology and the hot-pressing (HP) method, and the effects of sintering temperature on the microstructure, mechanical properties and fracture behavior were investigated. The HP alloys sintered at temperatures below 1400 °C are composed of Nbss (Nb solid solution), Nb3Si and Nb5Si3 phases. When the sintering temperature reaches 1450 °C, the Nb3Si phase is completely decomposed into Nbss and Nb5Si3 phases. Meanwhile, the microstructure coarsens significantly. Compared with the cast alloy, the HP alloy shows better mechanical properties. The fracture toughness of the alloy sintered at 1400 °C reaches 20.2 MPa·m1/2, which exceeds the application threshold. The main reason for the highest fracture toughness is attributed to the decomposition of large-sized brittle Nb3Si phase and the formation of a fine microstructure, which greatly increases the number of phase interfaces and improves the chance of crack deflection. In addition, the reduction in the size and content of silicides also reduces their plastic constraints on the ductile Nbss phase.

Decomposition of waterside plants greatly affects the transformation and mobility of sedimentary antimony in water–sediment systems after emergency treatment: A microcosm study

Polyferric sulfate (PFS) coagulation has proven to be effective in addressing antimony (Sb) water pollution accidents; however, the impact of waterside plant decomposition on its effectiveness has not been adequately elucidated. This study investigated the effects of Alternanthera philoxeroides (AP) and Digitaria sanguinalis (DS) decomposition on Sb cycling after PFS treatment. Without plant decomposition, the Fe(OH)3 hydrolysate-associated Sb remained stable, and the sediment continued to exhibit Sb sink properties. Plant residue decomposition facilitated sedimentary Sb release, and DS decomposition had a greater impact than AP decomposition. The strong decomposition phases triggered abiotic/biotic reduction processes, leading to Fe(OH)3 dissolution and subsequent Sb(V) release. Concurrently, sulfate reduction and dissolved organic matter (DOM) release regulated Sb mobility. In addition, Sb(V) reduction occurred, and Sb(III) was elevated in the overlying water. The Sb(III) levels gradually decreased during the later aerobic stages, however, did not completely disappear within a short timeframe. Furthermore, the role of the sediment as an Sb sink was significantly hindered, maintaining relatively high levels of dissolved Sb. Sedimentary Sb speciation analysis revealed that plant decomposition induced a shift in Fe-oxyhydroxide-bound Sb to more bioavailable and stable fractions. Our results indicate that plant residue decomposition easily deteriorates PFS efficiency and increases the risk of secondary Sb pollution in water–sediment systems.

The equivalence of titanium alloys defined via β phase decomposition paths

The equivalence of titanium alloys defined via β phase decomposition paths

Effect and mechanism of graphite addition on microstructures and hydrogen storage properties of Mg–Y–Zn alloy

In this work, the Mg-9.1Y-1.0Zn alloy are prepared by semi-continuous casting, and then mechanical milled with graphite. The microstructures and hydrogen storage properties of milled composite are systematically studied. The results show that the as-cast Mg-9.1Y-1.0Zn alloy exhibits serious agglomeration after milling. The addition of graphite significantly restrains the agglomeration of alloy and further refines the particles. Compared with as-cast Mg-9.1Y-1.0Zn alloy, the hydrogen storage properties of Mg-9.1Y-1.0Zn alloy milled with graphite is greatly improved. It needs only three times activation to be fully activated and its maximum hydrogen storage capacity is about 6.7 wt%. Besides, its dehydrogenation activation energy is decreased by about 40 kJ mol−1 relative to as-cast Mg-9.1Y-1.0Zn alloy. During hydrogen absorption and desorption, the stable YH2 hydride is generated by the disproportionation decomposition of LPSO phase. The graphite and in-situ formed YH2 present the synergistic confinement and catalysis effects on the milled Mg–Y–Zn alloy particles, which is conductive to the enhancment of hydrogen storage properties.

Tuned Reactivity at the Lithium Metal – Argyrodite Solid State Electrolyte Interphase

Thin intermetallic Li2Te–LiTe3 bilayer (0.75 mm) derived from 2D tellurene stabilizes solid electrolyte interphase (SEI) of lithium metal and argyrodite (LPSCl, Li6PS5Cl) solid-state electrolyte (SSE). Tellurene is loaded onto standard battery separator and reacted with lithium through single-pass mechanical rolling, or transferred directly to SSE surface by pressing. State-of-the-art electrochemical performance is achieved, e.g. symmetric cell stable for 300 cycles (1800 hours) at 1 mA cm-2 and 3 mAh cm-2 (25% DOD, 60 mm foil). Cryo-FIB sectioning and Raman mapping demonstrate that Li2Te–LiTe3 bilayer impedes SSE decomposition. The unmodified Li–LPSCl interphase is electrochemically unstable with geometrically heterogeneous reduction decomposition reaction front that extends deep into the SSE. Decomposition drives voiding in Li metal due to its high flux to the reaction front, as well as voiding in the SSE due to the associated volume changes. Analysis of cycled SSEs found no evidence for pristine (unreacted) lithium metal filaments/dendrites, implying failure driven by decomposition phases with sufficient electrical conductivity that span electrolyte thickness. Density Functional Theory (DFT) calculations clarify thermodynamic stability, interfacial adhesion, and electronic transport properties of interphases, while mesoscale modeling examines interrelations between reaction front heterogeneity (SEI heterogeneity), current distribution and localized chemo-mechanical stresses.

Producing hip implants of titanium alloys by additive manufacturing

Additive manufacturing (AM) technologies, in particular Selective Laser Melting (SLM) allows the production of complex-shaped individual implants from titanium alloys with high biocompatibility, mechanical properties, and improved osseointegration by surface texturing. In this work, the possibility of producing a custom-made hip implant from Ti-6Al-4V powder according to the data acquired via computed tomography of the patient is shown. Different heat treatments were applied in order to achieve better combination of tensile strength and elongation by partial decomposition of the martensitic phase. The implant was installed to the patient, postoperative supervision has shown good results, and the patient is able to move with the installed implant. A successful case of applying AM for producing custom hip implant is demonstrated in the paper. Using AM allowed the production of a custom-made hip implant in a short time and decreases the operation time and lessens the risk of infection ingress.

Nano-, micro- and macro-indentation tests of thermal spray WC-Ni coatings with lamellar microstructure at different particle deposition temperatures

The mechanical properties of WC-Ni coatings by HVOF thermal spraying were comprehensively evaluated by indentation tests at a wide load range of 10−1-103 N, i.e. nano-, micro- and macro-indentations. The correlation between process parameters and coating microstructure and mechanical properties was characterized via particle deposition temperature. The coating microstructure changes in reduced porosity, enhanced WC phase decomposition and better splats flattening were correlated to the particle deposition temperature rising. A porosity divergence between coating surface and cross-section was found as a quantitative anisotropy indicator to coating intrinsic lamellar microstructure formed by the splats flattening and piling up. Considering the lamellar microstructure, indentation responses on coating surface and cross-section were compared for hardness and elastic modulus evaluation below 3 N. The surface hardness is higher than that of cross-section, and both increased correlatively to the particle deposition temperature rising except for the almost constant surface hardness below 1 N. An analogous particle temperature-dependent behavior was also manifested for the elastic modulus by nano-indentation below 1 N. Interestingly, the elastic modulus by coating surface micro-indentation at 30 N presented identical particle temperature dependence to that by coating cross-section nano-indentation, both consistently representing the overall coating elastic modulus change trend verified by non-destructive ultrasonic test. Indentation fracture toughness on coating surface under 1.96 kN and on coating cross-section under 49 N was comparatively evaluated, and the values had a reverse trend of dependence on the particle deposition temperature. The particle-deposition-temperature dependent mechanical properties were interpreted by the coating intra-splats and inter-splats defects reduction with enhanced carbide-metal bonding essentially determined by the melting state of the metal binder phase, providing an insight to utilize indentation tests for characterizing thermal spray coatings.

A high-speed method to obtain Ni-Zn ferrite nanoparticles by microwave hydrotalcite decomposition for magnetic applications

Nanoparticles of Zn0.375Ni0.625Fe2O4 ferrite were successfully synthesized using an innovative, rapid, and efficient synthesis method based on microwave-assisted hydrotalcite decomposition, enabling nanoparticle crystallization in less than 15 minutes. A single composition was studied to better assess the impact of the synthesis method on structural, morphological, and magnetic properties. This new synthesis route was compared with the traditional ceramic method. The prepared hydrotalcite was analyzed by high-resolution transmission electron microscopy (HRTEM), identifying hydrotalcite diffraction planes consistent with selected area electron diffraction (SAED) and X-ray diffraction (XRD) patterns. The decomposition phases of the hydrotalcite were identified by simultaneous thermogravimetric and differential thermal analysis (DTA/TG). After hydrotalcite decomposition, the ferrite obtained was analyzed by XRD, confirming a single-phase cubic structure. Scanning electron microscopy (SEM) micrographs revealed nanoparticles less than 100 nm in size with the new method and larger than 2 µm with the traditional route. At a temperature of 5 K, the M-H graph obtained with a superconducting quantum interference device (SQUID) indicated that the spinel-type ferrite exhibited a smooth ferrimagnetic behavior, which was also corroborated by electron paramagnetic resonance (EPR). Magnetic saturation values of 105.73 emu/g were obtained in the synthesis microwave-assisted hydrotalcite decomposition and 51.49 emu/g in the traditional synthesis, representing an increase of over 100 %. The two synthesis methods were also compared using density functional theory (DFT) calculations, confirming the influence of morphology on magnetic properties, obtained thanks to different synthesis methods. These results indicate that the synthesized Ni-Zn spinel ferrite nanoparticles can be used in high-frequency applications, such as ceramic induction plates.

Effect of different boundary conditions on the combustion properties and fire characteristics of typical woods

To provide guidance on the bioenergy potential of wood and its fire spread numerical simulation, insights into the combustion properties and fire characteristics of one hardwood (sassafras) and two softwoods (pine and fir) were investigated. The effect of different boundary conditions are focused. The condensed phase decomposition in thermogravimetric analysis indicated that the main degradation processes for all wood combustion could be divided into two stages, and the corresponding demarcation point of conversion rate is 0.4 and 0.35 for hardwood and softwood, respectively. Three specific regions could further be established based on the activation energies variations in Stage Ⅰ. The governing reaction mechanism of sassafras wood is determined to be the diffusion model connect with order-based model, while the reaction mechanism of softwoods (pine and fir) can be considered as the reaction order (1st to three-halves) type followed by diffusion model. The gas phase flaming in FPA combustion experiments suggest that fir and pine wood have a faster charring rate and produce less CO and CO2 during pyrolysis and combustion. Sassafras requires more time to be ignited owing to its high density, which causes higher thermal inertia therefore decelerating the temperature increase on the sample surface. In addition, the dense structure of sassafras leads to an early appearance of the second HRR and MLR peaks. As hardwood has a higher density than softwood, the thermal insulation in hardwood delays char cracking on sassafras wood surface and enhances the duration between ignition and flameout. Such findings should provide guidance for wood combustion modeling and flame spread simulation in future works.

Microstructure evolution of diboride and carbide phases in platelets-toughened (Zr, Ti)C-(Ti, Zr)B2 ceramics via reaction pressureless sintering

Fully dense (Zr, Ti)C-(Ti, Zr)B2 composites were sintered via reactive pressureless sintering of ZrB2 and TiC based on the in-situ reaction and solid solution coupling effects. The effects of TiC content and sintering temperature on microstructure evolution and mechanical properties were explored. Elongated (Ti, Zr)B2 platelets were observed, stemming from the in-situ reaction between ZrB2 and TiC, and exhibited a high aspect ratio with the increase of TiC content. Besides, phase decomposition structures featuring semi-coherent interfaces were identified in the ZrB2-70mol.% TiC system sintered at 2200 °C, attributed to the chemical miscibility gap. High values of hardness (27.0 GPa), flexural strength (533 MPa), and fracture toughness (4.6 MPa m1/2) are found in ZrB2-70 mol.% TiC composite sintered at 2200 °C. The low porosity, solid solution strengthening, grain refinement caused by carbide phase decomposition, and high dislocation densities and strain concentration at the semi-coherent interfaces of carbide phase decomposed structures play an important role on hardening and strengthening. Furthermore, the presence of in-situ synthesized (Ti, Zr)B2 platelets with a high aspect ratio significantly contributes to toughening.

Microstructural evolution and phase transformation of cansas 3303 SiC fibers during thermal shock at 1200 °C

A self-built automatic platform was built to evaluate the thermal shock performances of Cansas-III SiC fibers at 1200 °C in air up to 500 cycles, the corresponding oxidation and damage mechanisms were then revealed. The results showed that oxide scale was formed during thermal shock with a thickness of about 1 μm, the core was not oxidized via its protection. The fiber roughness increased before 100 cycles due to the decomposition of the amorphous SiCxOy phase, and then decreased as the formation of oxide scale. Within Cansas-III SiC fibers, structural defects of free carbon increased as the increasing ID/IG values, in addition, the TO peak shifted to the left, which both demonstrated that the relative movements occurred among SiC grains and residual stresses were then emerged. To clarify the axis and radial cracking of the oxide scale, a modified formulation considering nonzero shear strain components was then proposed to calculate the related residual stresses. The peeling and cracking of the oxide scale was ascribed to the residual stresses of GPa level among SiC grains and the thermal expansion mismatch between the oxide scale and the core.

Thermal performance of MK/FA geopolymers: Unveiling the role of FA, equivalent Na2O and modulus

This paper investigates the thermal stability of metakaolin/fly ash (MK/FA) based geopolymers at elevated temperature of 500℃ and 800℃. The thermal stability of geopolymers is evaluated from the following aspects: apparent morphology, residual compressive strength, volumetric shrinkage, and microstructure. The results show that the incorporation of FA contributes to the reduction of specimen cracking while the increasing of equivalent Na2O leads to severe cracking. After experiencing 800°C, the compressive strength of all specimens remains above 70 % of that at room temperature, and the specimen with high equivalent Na2O exhibits higher compressive strength. The XRD and FTIR results indicate that the chemical component of most specimens remains stable at elevated temperatures without decomposition and formation of new crystalline phases. However, the MK/FA based geopolymer exhibit considerable volume shrinkage at elevated temperatures. The shrinkage ranges from 3.2 % to 4.9 % at 500°C and 5.1–14.2 % at 800°C for different specimens. The increase of equivalent Na2O from 8 % to 16 % results in a 174.8 % increase of shrinkage. Overall, MK/FA based geopolymers exhibit convincing thermal performance, and the specimens exhibit higher residual compressive strength and chemical stability after exposure to elevated temperatures.

Microbial quality and macronutrient of vermicompost produced by Eisenia fetida in dairy wastewater solids

Abstract. Marlina ET, Hidayati YA, Harlia E, Badruzzaman DZ, Meynadhea N, Rahayu NA. 2024. Microbial quality and macronutrient of vermicompost produced by Eisenia fetida in dairy wastewater solids. Biodiversitas 25: 2729-2737. Dairy Wastewater Solids (DWS) contain enough nutrients for the growth of earthworms and utilize the nutritional requirements of livestock waste for growth. The growth of earthworms affects the quality of vermicompost or castings that are useful as organic fertilizers. This research aimed to determine the growth of Eisenia fertida using DWS as a growth medium, and its effect on the quality of vermicompost produced. The organic material decomposed in DWS by indigenous microorganisms and earthworms can convert DWS into organic fertilizer through composting. Rice straw was added as a carbon source to obtain the ideal C/N ratio for the growth of decomposing microorganisms. Good growth of decomposer microorganisms can increase the availability of nutrients in DWS as a source of plant nutrition. E. fetida was used in vermicomposting for 14 days after the initial decomposition phase had passed. This research used the experimental method of Completely Randomized Design (CRD) with three stocking density treatments (T1: 6.6 g/L; T2: 13.3 g/L; T3: 20.0 g/L ) and six replications. The results showed that higher stocking density promoted an increase in the biomass weight of earthworms. Various indigenous microorganisms act as decomposers and work with earthworms to convert organic matter into inorganic matter as a plant nutrient. The stocking density treatment had no significant effect on vermicompost production, total nitrogen content, and P2O5 vermicompost but had a significant effect on K2O, Ca, Mg, population of Nitrogen-Fixing Bacteria (NFB) and Phosphate-Solubilizing Bacteria (PSB). Vermicomposting, DWS, and rice straw mixture produced vermicompost with high functional microbial and macronutrient concentrations.

Achieving superior compressive strength-ductility synergy in a novel ODS-CrFeNi/AlCrFeNi heterostructured high-entropy composite

A novel high-entropy heterostructured composite (ODS-CrFeNi/AlCrFeNi) was fabricated by powder metallurgy method. The microstructure and mechanical properties of the composites with various sintering temperatures (950 °C to 1100 °C) and various addition amounts (0% to 20%) of FCC-structured reinforcing phase (ODS-CrFeNi) were investigated. The results revealed a reduction in porosity and an increase in relative density, reaching up to 99% with increasing sintering temperature. The optimal sintering temperature is 1100 °C. In the composites with the addition of 5% and 10% ODS-CrFeNi reinforced phases, spinodal decomposition (SD), forming BCC and B2 phases, takes place both in the matrix and in the reinforcing phase. As the reinforcing phase content is increased to 15% and 20%, SD occurs exclusively in the matrix while is suppressed in the reinforcing phase. The reinforcing phase consists of hard BCC structured Cr rich phases and soft FCC-structured FeNi phases, forming a gradient network structure. The composite with 15% reinforcing phase exhibits high hardness of 841 HV and compressive yield strength, ultimate strength and strain of 6960 MPa, 7690 MPa and 15.5%, respectively, which are 2.5, 2.7 and 1.9 times higher than those of the reference alloys (without reinforcing phase). The excellent strength-ductility synergy originates from the unique gradient network structure formed in the reinforcing phase, i.e. complex heterogeneous structure, which results in hetero-deformation induced (HDI) strengthening for higher strength and HDI strain hardening for higher ductility.

Improving the strength and maintaining good ductility of as-forged Ti6Al4V alloy by regulating the microstructural defects

Solution-aging treatment is a conventional method for enhancing the strength of titanium alloys contributed by the decomposition of metastable phases, like martensite. The traditional viewpoint suggests that the martensite transformation occurring after water quenching does not significantly contribute to the strengthening of titanium alloy and this perspective actually overlooks the high strength resulting from the high-density defects formed in the martensite microstructure due to rapid cooling. So, previous studies have not fully taken advantages of the excellent strengthening capability of martensite. This study adopted a technique which combined solid solution and incomplete aging treatment to control the decomposition behavior of martensite and as a result, the strength of the as-forged Ti-6Al-4V (TC4) alloy had been obviously improved and good ductility had been maintained. Furthermore, the changes of phase structure and microstructural defects in TC4 titanium alloy during solution and aging process have been detailly studied by XRD refinement, EBSD, and TEM. Specifically, the highest tensile strength increased by 28.8 % which could reach 1224 MPa, and the elongation at fracture could still remain at 13 %. The reason is as follows. The formation of martensite after water quenching led to a substantial increase in internal microstructural defects, which were partly retained during the subsequent aging process because of lower temperature and short aging time, and the remaining martensite and microstructural defects can help maintain high strength. What's more, a small part of defects disappeared during this incomplete aging process due to martensite decomposition and recovery, which was beneficial to ductility.

Investigation of phase separation mechanism in AlCoCrFeMo0.05Ni2 high-entropy alloy by first-principles calculations

AlCoCrFeMo0.05Ni2 high-entropy alloy (HEA) has great potential for high-temperature applications. However, its FCC matrix will decompose during annealing, which seriously limits its high-temperature applications. Here, the lattice distortion, Gibbs free energy change, phonon spectra, density of states, and bond length distribution of the FCC matrix were calculated by first-principles calculations. The findings indicate that the primary barrier to the formation of a single homogeneous solid solution in the alloy is more closely associated with Gibbs free energy rather than the degree of lattice distortion. The vibration frequency of Al is not in sync with the overall structure, making it prone to desolvation at elevated temperatures. Furthermore, an analysis of bond lengths reveals that the Al–Ni bond length is significantly shorter than the theoretical value, facilitating the formation of a (Ni, Al)-rich phase. In contrast, the longer bond lengths of Al–Cr and Al–Mo facilitate the detachment of Cr and Mo from the (Ni, Al)-rich phase, resulting in the formation of (Cr, Mo)-rich phase. This in-depth investigation sheds light on the phase decomposition mechanism of high-entropy alloys, offering valuable insights for future research in this field.

Effect of the accelerated aging process on the thermal decomposition of LiAlH4-based composite solid propellants

In the present work, a study was carried out on the effect of the accelerated aging process on the thermal decomposition of two composite solid propellants based on ammonium perchlorate (AP) and hydroxy‑terminated polybutadiene (HTPB). The first one (CP1) was enriched with aluminum (Al) powders, while the second (CP2) contained a mixture of aluminum and lithium alanate (LiAlH4) as a high-energy fuel additive. The thermal properties of the investigated propellant samples were determined using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The obtained results clearly demonstrated the effect of the aging process on the thermal degradation of the aged samples compared to the unaged ones, by shifting the temperature peaks of their main decomposition step to lower temperatures with a decrease in their DSC heat release. In addition, the residual unburnt propellant was increased, particularly for the complex metal hydride-based propellant. Kinetic modeling of the main thermal degradation phase, applying two advanced isoconversional methods, revealed a significant decrease in activation energy for the aged samples. Furthermore, the three-dimensional diffusion model involved during the investigated decomposition phase of the unaged samples was changed to a random nucleation model after 60 days of aging time.