Nano-sized Carbide Research Articles

Synthesis and Purification of Nano-sized Titanium Carbide Particles through Vacuum Carbothermal Reduction for enhanced Mechanical, Microstructural Morphology, and Tribological Properties in Friction Stir Processed A356-based Aluminum Composites

This study focused on the synthesis and purification of nano-sized titanium carbide (TiC) particles through vacuum carbothermal reduction under a hydrogen/argon atmosphere. The process involved the production of carbon-coated titanium precursors, followed by heating under vacuum conditions at 1500°C for 2.5 hours. The resulting products underwent additional treatment in either a hydrogen/argon (1:1) mixed gas or pure hydrogen gas. Experimental findings revealed that TiC powders exhibiting a single phase are obtained within a molar ratio of Ti to C ranging from 1:2 to 1:4. Adjusting the molar ratio of Ti/C in the precursors allowed for controlled variation in the particle size of the synthesized TiC powders, ranging from 50 to 80 nm. Treatment in hydrogen/argon mixed gas at 850°C for 3 hours resulted in TiC products with an impressive purity of 99.40%. The subsequent incorporation of 5% Nano-TiC-3 (Ti to C ranging from 1:3) as reinforcement into an aluminum alloy by Friction stir process technique demonstrated a remarkable 19.41% improvement in tensile strength, highlighting the efficacy of this specific reinforcement. The nano-TiC-3 reinforced composite exhibited uniform distribution without porosity. Additionally, a notable 50.81% improvement in hardness and the best wear resistance were observed for the 5% Nano-TiC-3 reinforced aluminum composite. This comprehensive study contributes valuable insights into the synthesis, purification, and application of nano-sized TiC particles, paving the way for the development of high-performance aluminum-based composites with enhanced mechanical and tribological properties.

Realizing strength-ductility combination of Ni-12Mo-7Cr-2Nb based superalloy via nano-sized MC carbides at stacking faults and grain boundaries

Developing corrosion-resistant alloys with the outstanding strength-ductility combination at elevated temperatures are highly desirable for molten salt reactor (MSR) applications. In this study, by appropriate preaging process, the yield strength and elongation of one newly developed Ni-12Mo-7Cr-2Nb based superalloy at high temperatures respectively increase by ∼50 % and ∼100 % as compared with the solid-solution state. This preaged alloy exhibits the excellent strength and overcomes the intermediate temperature embrittlement problem as compared with other alloys. Microstructure observations indicate that the strengthening and ductility improvement are related to the formation of nano-sized MC carbides. After preaging process, the extrinsic stacking faults are formed along {111} close-packed planes and decorated with ultra-dense MC carbide particles, thus are called as stacking faults precipitates (SFPs). SFPs contribute to the precipitation strengthening by the complex interaction with dislocations. Surprisingly, the SFPs exhibits the better strengthening effect than the uniformly dispersed MC carbides with the same volume fraction and size. Furthermore, it was found that the “pseudo-continuous” intergranular MC carbide particles are beneficial to the high-temperature ductility, although the similar intergranular precipitates were widely regarded as harmful in other studies. Using crystal plasticity finite element method, it was proved that the strain concentration at the triple junctions would be obviously alleviated because the intergranular MC carbide particles can suppress grain boundary sliding. If tested at 750 °C, the intergranular MC carbide particles would trigger the particle-stimulated nucleation and lead to the local dynamic recrystallization at grain boundaries and crack tips. These small recrystallized grains can suppress crack propagation and bring about the improvement in ductility in the aged alloy.

Tailoring microstructural stability and stress rupture properties of a solid-solution strengthened Fe-Ni-based superalloy via niobium addition

The influence of niobium (Nb) addition on the microstructural stability and 750 °C/135 MPa stress rupture properties of a solid-solution strengthened Fe-Ni-based superalloy designed for fourth-generation (Gen IV) nuclear reactors was systematically studied. The results showed that the stress rupture life first increased and then decreased with the increase of Nb content. The alloy with the addition of 0.5 wt% Nb exhibited the best stress rupture properties, with a stress rupture life of 164 h. Compared to Nb-free alloy, the stress rupture life has been increased by 382 %. The enhanced creep performance of this alloy was closely related to its excellent high-temperature microstructural stability, which can be explained as follows: homogeneous and optimal grain size distribution, elemental Nb provided good solid-solution strengthening effects, fine granular secondary carbides relieved stress concentration and strengthened grain boundaries (GBs), dynamic precipitation of nano-sized NbC carbides effectively pined dislocations. Dynamic recrystallization (DRX) behavior can be observed in all alloys. The mechanisms related to DRX behavior were discussed, and it was deemed that the smaller average grain size, higher blocky NbC volume fraction, and increased stacking-fault energy (SFE) may be responsible for the facilitated DRX in the alloy with higher Nb content, which greatly caused local softening and consequently, decreasing the creep resistance of the alloy. Important guidance for the further design and development of γ′-free Fe-Ni-based superalloys for Gen IV nuclear reactors with good high-temperature microstructural stability and creep performance could be summarized from the present study.

Strength stability at high temperatures for additively manufactured alumina forming austenitic alloy

Several fast-spectrum nuclear reactors designed to generate high power (∼450 MWe) rely on forced convection of media such as supercritical CO2, sodium, or liquid lead to cool the nuclear core, operating at temperatures up to 600 °C. Cost-effective, high-strength Fe-based alumina forming austenitic (AFA) alloys are a promising candidate for the fabrication of critical nuclear components. This study investigated laser powder bed fusion (LPBF) processing of an AFA alloy composition optimized for improved creep resistance. Electron microscopy revealed an elongated grain structure along the build direction with a fine sub-grain cellular structure decorated with (Cr,Fe,Nb)23C6 carbide precipitates at the intercellular boundaries. At temperatures of 20–900 °C, the LPBF alloy's superior tensile properties compared to its arc-melted counterpart and other advanced steels (e.g., SS316) were attributed to the distribution of nano-sized carbide precipitates, whereas the high ductility was attributed to the LPBF alloy's elongated grain structure.

Microstructural characterization of AISI 440C stainless tool steel fabricated by laser powder bed fusion

Abstract The microstructure of a stainless tool steel AISI 440C fabricated by laser powder bed fusion (L-PBF) without pre-heating of the build plate was characterized by multi-scale experimental methods. In combination with thermodynamic calculations, the solidification and cooling-down procedures were analyzed with the intention to understand the cracking behavior of high carbon tool steels processed by L-PBF. The results showed a fully austenitic structure in the as-built sample with sub-micro cellular structures and nano-sized carbides decorating the cell walls. Significant segregation exists merely at the intersection of cell walls while it is absent along high angle grain boundaries. Factors contributing to crack-free AISI 440C are discussed, providing guidelines for future L-PBF fabrication of high-carbon tool steels.

Tribology of Mg-B4C nanocomposites fabricated following powder metallurgy route

In this experimental work, magnesium nanocomposite reinforced with various percentage of boron carbide (0.5%, 1.0%, 1.5%, 2.0% by volume) is fabricated using conventional powder metallurgy technique. Characterisation and wear test of the fabricated composite have been performed using scanning electron microscopy, tribology test monitor respectively. It is observed that addition of B4C increases the hardness and wear resistance linearly. Addition of 2% B4C produces the hardness of the nanocomposites as high as 57.93 ± 4.9 Hv. Furthermore, the nanocomposites displayed improved wear resistance and lower friction coefficient compared to the base magnesium. The influence of sliding speed on these properties has been systematically presented. The paper provides an in-depth exploration of wear mechanisms through a meticulous analysis of SEM micrographs of worn surfaces. This work offers valuable insights into the microstructural characteristics and tribological behaviour of Mg-B4C nanocomposites. These findings underscore the potential application of Mg-B4C nanocomposites in the development of lightweight wear-resistant materials. The impact of incorporating minute amounts of nano-sized boron carbide into Mg, on its behaviour under small loads and repeated scratching has been investigated in this study. Moreover, introspection of the wear mechanisms and the effectiveness of the powder metallurgy technique in fabricating composite materials is presented.

Microstructure and high-temperature tribological behaviours of nano-HfC reinforced Inconel 625 composite coating by plasma-transferred arc welding

The study involved plasma arc transfer welding (PTAW) for preparing coatings of Inconel 625 alloys that contained different amounts of nano-sized hafnium carbide (nano-HfC) particles. The impact of nano-HfC on the microstructure evolution and mechanical properties of PTAWed Inconel 625 were investigated. The research reveals that nano-HfC decomposes during the high-temperature plasma arc process and then react with O element to generate nano-HfO2. These HfO2 can serve as nucleation sites for MC carbides, which restricts the growth of secondary dendrite arms, leading to a more disordered grain growth direction. Simultaneously, the decomposition of HfC can increase the C/Nb ratio of the matrix, effectively suppressing Laves phase formation while encouraging the development of MC carbides. Compared with IN625, the wear rate of composites at room temperature and 600 °C were decreased. Notably, at 600 °C, the wear rate of the coating with 0.5 wt% HfC is the lowest among all the samples, as reflected by a noteworthy reduction in wear rate of 50 %. This is mainly attributed to the refinement of γ matrix, reduction of Laves phase as well as precipitation of the fine-sized MC carbides. This work illustrates that adding nano-HfC is an effective way to improve the wear resistance of the PTAWed Inconel 625.

Annealing response and yielding behavior of cold rolled advanced HSLA steels

High-strength low-alloy (HSLA) steel is well established in car body manufacturing. They comprise a lean low-carbon alloy concept and can be produced by a wide variety of processing routes. However, cold-rolled HSLA steels are typically limited to a yield strength of 460 MPa by current standards. This research work will present a concept of extending the yield strength range of cold-rolled HSLA steels to above 500 MPa. A key aspect is to find the right balance between recovery and recrystallization of the cold rolled matrix during the annealing stage thereby mitigating the influence of solute and precipitated niobium. Additional solute draging power was introduced by alloying molybdenum to one of the investigated steels. A detailed microstructural analysis using transmission electron microscopy revealed that under recovery annealing conditions an ultrafine-grained microstructure with ferrite grain sizes between 0.5 and 1 μm can be established leading to large strength contribution via the Hall-Petch relationship. Strength losses related to partial recrystallization can be recovered to an extent of around 200 MPa by the precipitation of nano-sized niobium carbide particles. It is demonstrated that the presence of niobium and molybdenum in solute condition have the most prominent influence on obstructing recrystallization via solute drag. It is furthermore shown that the magnitude of precipitation strengthening correlates with the Lüders strain. The analysis of the work hardening behavior indicated that the n-value in ultrafine-grained condition approaches a lower limit value of 0.03 and raises to above 0.2 with progressing recrystallization as well as precipitation strengthening. The detailed evaluation of the tensile characteristics indicates that the strength limit for these HSLA steels ranging between 830 and 880 MPa is reached when the average grain size is reduced to 0.46 μm. The results of this study used to define robust processing conditions to securely produce steel grades in the 600–800 MPa yield strength range.

Influence of nano-sized WC addition on the microstructure, residual stress, and tribological properties of WC-Co HVAF-sprayed coatings

It has recently been proposed to modify conventional WC-Co coatings with nano-sized particles to improve their properties. Modification of the coatings with nano-sized carbides may provide higher wear resistance or phase composition stability. This work characterized the changes in the residual stresses induced by introducing WC nanoparticles into a WC-Co coating and the resulting change in their sliding wear behavior.A powder mixture consisting of agglomerated and sintered WC-17Co feedstock powder and 5 % nano-sized WC was deposited on a carbon steel substrate using the High Velocity Air Fuel (HVAF) process. Microstructural characterization using scanning electron microscopy and EBSD confirmed that nano-sized WC particles were embedded in the coatings after the spraying process, primarily along the boundaries of the WC-Co lamellae. This resulted in an enhancement of microhardness, indentation fracture toughness, and dry sliding wear resistance, evaluated via ball-on-disk tests against Al2O3 counterparts. Residual stresses in the coatings were also measured by XRD using the sin2ψ method. The normal stress along the torch movement direction decreased significantly when nano-sized WC was added. The addition of nanoparticles also caused a slight decrease in the normal stress perpendicular to the torch movement.

Green synthesis of nanosized Tantalum carbide (TaC) via natural polymer/tantalum oxide hybrid composites: A sustainable approach towards enhanced processing and properties

This study provides a green method for producing nanosized tantalum carbide (TaC) by pyrolyzing natural polymer (Gum karaya)/tantalum oxide hybrid composites, which is both sustainable and environmentally benign. The carbothermal reduction, carried out at 1500 °C, produces cubic TaC with a cell constant of ao=4.451 Å. The synthesised TaC reveals a near spherical morphology with an average size of 200 nm, far smaller than commercial TaC. The synthesised TaC displays a beginning oxidation temperature of 420 °C, as compared to the commercial powder (500 °C). Incorporating 5 wt% as-synthesized TaC to commercial TaC results in an impressive relative density of 98%, demonstrating the TaC ability as an excellent sintering aid. This green synthesis not only reduces the environmental impact of conventional methods, but also provides improved characteristics of nanosized TaC for advanced applications, contributing to the field of green nanotechnology by emphasizing safer production methods.

Enhancing the strength-ductility synergy in hot-forged Fe50Mn30Co10Cr10 high entropy alloy (HEA) through carbon additions

In this work, we systematically investigated the effect of carbon additions on the microstructure and room temperature mechanical properties of hot-forged Fe50Mn30Co10Cr10 HEA. The different carbon contents were introduced to Fe50-xMn30Co10Cr10Cx (x = 1, 2.5, 6 at.%, hereinafter, referred as C1, C2.5 and C6, respectively) HEAs to enhance the strength-ductility synergy by triggering the multiple strengthening mechanisms. The results showed that the grain sizes were decreased with increasing of carbon content, while a high fraction of mechanical twins ∼45% were generated in C2.5 HEA, and their fractions were ∼35% in C1 and C6 HEAs. Moreover, the discrete nano-sized M23C6 carbides in C2.5 HEA were transformed into continuous mico-sized M23C6 carbides along the grain boundaries in C6 HEA. Therefore, C2.5 HEA possessed high yield strength of 584 MPa, tensile strength of 1.03 GPa and outstanding ductility of 68%, i-e., breaking the strength-ductility paradox. A highest yield strength of∼662 MPa and tensile strength of more than 1 GPa were observed for C6HEA with refine grains, although the ductility was only ∼10%, which indicated that the massive carbon addition could effectively enhanced the strength of HEA but at the cost of ductility due to the presence of coarse M23C6 carbide precipitation. The enhanced mechanical properties of studied HEAs are mainly ascribed to the contribution of multiple strengthening mechanisms including precipitation, grain boundary, dislocation and interstitial solid solution strengthening.

Break the strength and ductility trade-off in novel NbC reinforced Fe40.5(CoCr)25Mn17.5Ni10Si5 high entropy alloy

In this study, a novel NbC reinforced Fe40.5(CoCr)25Mn17.5Ni10Si5 high entropy alloy (HEA) was designed, which exhibits high strength and ductility at room temperature. This alloy was prepared through hot forging and annealing treatments, which exhibited the FCC microstructure with NbC and discrete nano-sized M23C6 carbides precipitation. The studied HEA retained a tensile strength of 863 MPa, and an outstanding ductility of 58 %. The microstructure evolution and deformation mechanisms were further investigated. The deformation mechanism was mainly governed by nano-scale defect heterogeneity of stacking faults (SFs), deformation twins and dislocations. The improved strength-ductility synergy is attributed to the formation of multiple SFs, deformation twining, dislocation cells, and nano-sized NbC precipitation. Moreover, the TEM observation elucidates the presence of chemical short-range order (SRO) domain in the studied HEA, which also has a major contribution in strength and ductility increment. The present findings shed light on developing the HEAs through proper compositional design and heat treatments, resulting in the combine effect of precipitation strengthening, SFs mediated plasticity, twinning induced plasticity (TWIP), and SRO effect.

Cryogenic Treatment of Martensitic Steels: Microstructural Fundamentals and Implications for Mechanical Properties and Wear and Corrosion Performance.

Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) formation of refined martensite coupled with an increased number of lattice defects, such as dislocations and twins, (iii) changes in the precipitation kinetics of nano-sized transient carbides during tempering, and (iv) an increase in the number of small globular carbides. These microstructural alterations are reflected in mechanical property improvements and better dimensional stability. A common consequence of cryogenic treatment is a significant increase in the wear resistance of steels. The current review deals with all of the mentioned microstructural changes as well as the variations in strength, toughness, wear performance, and corrosion resistance for a variety of iron alloys, such as carburising steels, hot work tool steels, bearing and eutectoid steels, and high-carbon and high-alloyed ledeburitic cold work tool steels.

Evolution from clusters to precipitates in niobium-micro-alloyed ferritic steel: A combined in situ scanning transmission electron microscopy and atomistic study

Nano-sized carbides are essential for strengthening steel. In this study, we examined the evolution of metal carbide (M-C) clusters (M = Ti and Nb) into MC precipitates within a ferrite matrix through a reverse Bain transformation at the atomic level using the first-principles method. Through in situ transmission electron microscopy, the evolution of the Nb-C cluster into an NbC precipitate was observed for the first time. The Nb-C cluster was confirmed to maintain coherence with a limited carbon content, assuming a disc-shaped form that grew in a specific direction owing to misfit strain upon reaching a critical size. Interface dislocations were also formed. The NbC precipitate formation was subsequently completed through additional carbon diffusion. The findings of this study indicate that MC precipitation in a ferrite matrix can be attained through coherent cluster evolution with a specific carbon content.

Enhanced strength ductility and wear resistance in a friction stir processing engineered AZ31B/TiC magnesium-based nanocomposites

ABSTRACT In the present investigation, efforts have been made to fabricate a magnesium-based AZ31B nanocomposite by integrating nano-sized titanium carbide (TiC) particles via utilising the friction stir processing (FSP) process. The primary objective of the research was to enhance the metallurgical, mechanical, and tribological properties of the base material while investigating the influence of secondary phase particles and various FSP parameters. The findings were rigorously validated through a comprehensive analysis, which encompassed the use of various testing apparatus, such as optical microscopy, field emission scanning microscopy, microhardness testers, tensile and compressive testing machines, along with fractography analysis for wear morphology and tensile properties. The results indicate that the nanocomposite produced under the conditions of a tool rotation speed of 1600 rpm and a transverse speed of 40 mm/min along with three number of FSP passes exhibits superior mechanical and tribological properties compared to both other developed composites and the base alloy. A significant enhancement of nearly 2.68 times in microhardness values along with simultaneous refinement in grain size up to 14.85 times was obtained. Ultimate tensile and compressive strengths report an impressive increase in values up to 2.16 and 1.6 times respectively when compared to the base metal. Furthermore, the tensile fracture behaviour of the base magnesium alloy indicated brittleness, while the AZ31B/TiC composite displayed a combination of ductile and brittle features. In terms of wear morphology, the base magnesium alloy exhibited adhesive and abrasive wear, while the composite demonstrated particle pull-out, delamination, and localised plastic deformation, with enhanced resistance to wear. These findings underscore the significant improvements achieved in mechanical and tribological properties, thus emphasising the novel contributions of this research to the field.

Microstructure and abrasive wear performance of a novel CALPHAD-inspired wear-resistant steel containing multiphase and multiscale carbides

The microstructure and abrasive wear performance of a novel wear-resistant steel designed based on the CALPHAD approach were characterized and evaluated. The steel exhibited distinct improvements over conventional high chromium cast iron through the precipitation of micron-sized M7C3 carbides from austenite via desolation transformation, resulting in a more uniform distribution with smaller sizes and desirable shapes. Moreover, the steel incorporated micron-sized carbides (M7C3, VC, and Mo2C) and submicron carbides (M7C3 and VC) as hard reinforcing phases, while nano-sized carbides (Mo2C, M7C3, and M3C) contributed to dispersion hardening. The wear resistance and impact-abrasive wear resistance of the steel were 1.8 times and 1.7 times superior to that of KmTBCr26 under identical wear conditions, respectively. These results indicated that the modified features of the micron-sized M7C3 carbides effectively mitigated undesirable phenomena such as cracking and spalling during the wear process, leading to improved impact-abrasive wear resistance in this steel. The exceptional wear resistance was attributed to the synergistic effect of multiphase and multiscale carbides, demonstrating the effectiveness and potential of CALPHAD-inspired design strategies in developing advanced wear-resistant materials.

First - Principles study of hydrogen - Carbide interaction in bcc Fe

Rapid developments in the field of hydrogen energy have prompted the need for safe and efficient hydrogen transportation and storage. Steels form the backbone of the current energy infrastructure and thus offer a fast and cost-effective solution. Their excellent mechanical properties are attributed to the underlying microstructure which comprises of finely dispersed nano-precipitates. However, one major factor restricting their application is their susceptibility to Hydrogen Embrittlement (HE). In the past decade, experimental and theoretical works have been carried out to understand if the nano-sized carbides can aid in reducing the susceptibility to HE along with providing strengthening. Within this ab-inito study, we investigated the effectiveness of fully coherent nano-carbides (i.e. TiC, VC and NbC) to limit the diffusible hydrogen content in bcc Fe. Our study revealed that the interplay between hydrogen and carbon vacancies, local atomic environment at interface as well as elastic strain fields at the interface can lead to significantly increased hydrogen solubilities. While in TiC, the deepest traps were found to be in the bulk of carbides, in VC and NbC, the elastic strain fields around the interface led to the strongest trapping. Further, the formation of a two-hydrogen-vacancy complex was found to be favourable in VC. Finally, the migration barriers for hydrogen trapping in bulk TiC as well as across the Fe/TiC coherent interface indicate that these deep traps in the form of carbon vacancies are fairly accessible.

Nano-TiC-reinforced 18Ni300 steel manufactured by Powder Bed Fusion-Laser Beam with improved wear resistance for mould inserts

In injection moulding, surfaces can be exposed to harsh working conditions, especially when polymers reinforced with abrasive glass fibres are used. Low carbon martensitic steels, such as maraging steels, are an excellent choice for demanding and complex mould inserts produced by Powder Bed Fusion-Laser Beam (PBF-LB). However, their wear resistance is lower than that of tool steels such as AISI D2 or H13, whose PBF-LB printability is challenging, due to their carbon content that makes them susceptible to cracking. In this study, an alternative material with high printability by PBF-LB was developed, by reinforcing maraging steel 18Ni300 with nano-sized titanium carbide (TiC). TiC-reinforced 18Ni300 nanocomposites showed an improvement in microhardness of up to 23% (730 HV2) after addition of 7.0 vol% TiC. Tribological tests against a polypropylene with 40 wt% glass fibres showed that the specific wear rate decreased by about an order of magnitude (to 0.32 × 10–6 mm3/N m) compared to the unreinforced maraging steel.Graphical

Multiphase precipitation behavior and tensile properties of a Fe-Mn-Al-Mo-C austenitic lightweight steel

In order to improve the strength and strain hardening rate, multiple precipitates were introduced by annealing at 850–950 °C and aging at 550 °C after hot or cold rolling in a Fe-26Mn-8Al-3Mo-1.2C austenitic lightweight steel. The results show that the combination of rolling, annealing at 850 °C and aging produces a microstructure consisting of nano-sized κ-carbides and Mo2C carbides within equiaxed austenite grains and submicron-sized Mo6C carbides along grain boundaries. Further increasing annealing temperature to 950 °C reduces the precipitation of Mo2C and decreases the density of dislocation. The yield strengths increase by ∼300–500 MPa, and ultimate tensile strengths increase by ∼200–400 MPa by comparison with the steel processing by solid solution and two-step aging. Cold rolling before heat treatments leads to an improvement in strength compared to hot rolling, mainly due to grain boundary strengthening and Mo2C precipitation strengthening. Decreasing annealing temperature after rolling from 950 to 850 °C increases strength primarily ascribed to Mo2C precipitation strengthening and dislocation strengthening. The introduction of a large number of fine Mo2C precipitates distributed evenly within the steel matrix through cold rolling and subsequent annealing at 850 °C increases the strain hardening rate effectively.

Insight into combustion characteristics of micro- and nano-sized boron carbide

The combustion characteristics of micro- and nano-sized boron carbide (B4C) powders were investigated to exploit the role of carbon atoms on combustion. Various combustion parameters had been evaluated for B4C powders. Results demonstrated a direct correlation between the gas oxide of carbon atoms with the morphology of condensed combustion products. The thrust generated when the gas diffused from the B4C matrix to the environment could not only disperse the burning B4C powder, but also break through the liquid oxide layer and leave holes on the surface of micro-sized B4C. The formed holes on the surface were considered oxygen diffusion channels to the interior of B4C particle, which accelerated the mass transfer rate and improved the oxidation efficiency. The evolution images of confined combustion and the characterizations of condensed combustion products suggested that the B4C powder released most of energy potential after stable combustion and transformed into boron oxide. Given the combustion process, the B4C powders exhibited the higher combustion heat and the larger peak area of combustion pressure than boron powders with similar diameter distribution, and the B4C powders in nano-sized generated strongest energy output among all samples.