Expanded Graphite Content Research Articles

Green Electromagnetic Interference Shielding Material Based on Thermally Expandable Microspheres.

With the aggravation of electromagnetic pollution, electromagnetic interference (EMI) shielding materials have received enormous attention. However, most of the current EMI shielding materials only focus on the shielding effectiveness (SE), neglecting the electromagnetic pollution brought by secondary reflection. In this work, a method of preparing absorption-dominated EMI shielding materials, which are also called green EMI materials, using thermally expandable microspheres (TEMs) and expanded graphite (EG), is proposed. The expansion of TEMs in the EG/waterborne polyurethane mixture can improve the impedance matching between the composite and air. When the content of TEMs is 5 wt % and the content of EG is 15 wt %, the EMI SE of the sample reaches 38.4 dB, and the average reflection power coefficient of this composite is 0.27, indicating that the material mainly shields electromagnetic waves through absorption. Meanwhile, the prepared material also exhibits good stability, maintaining outstanding EMI SE and low value of reflection power coefficient even after the compression-recovery test.

Cycle performance analysis of hybrid battery thermal management system coupling phase change material with liquid cooling for lithium-ion battery module operated at high C-rates

High performance battery thermal management system (BTMS) is urgently needed to satisfy the severe cooling demand of battery modules operated at high C-rates during continuous charging-discharging cycles. Hybrid BTMS coupling phase change material (PCM) with liquid cooling is a promising solution which attracts great attention in recent years. Here, cycle performance of the hybrid system is analyzed in detail via comparison with the pure PCM system to examine its reliability and demonstrate its superiority during continuous 3C-charging and 4C-discharging cycles. Effects of PCM melting temperature are studied and RT44HC is found a suitable PCM choice with appropriate melting temperature. Analysis of the first three cycles is proved important and basically sufficient as system thermal behavior stabilizes afterwards. Further, interacting mechanisms of expanded graphite (EG) content and battery distance on system cooling performance are elucidated and their possible combinations satisfying temperature requirements of battery module in both temperature rise and temperature uniformity are presented. Optimal combination of EG content and battery distance is 3 % and 3 mm. Effects of coolant velocity are also investigated and suitable velocity for the optimized hybrid system is set at 0.01 ms−1 to achieve balance between cooling performance and auxiliary energy cost.

The Effect of Expanded Graphite Content on the Thermal Properties of Fatty Acid Composite Materials for Thermal Energy Storage.

The mass content of expanded graphite (EG) in fatty acid/expanded graphite composite phase-change materials (CPCMs) affects their thermal properties. In this study, a series of capric-myristic acid/expanded graphite CPCMs with different EG mass content (1%, 3%, 5%, 8%, 12%, 16%, and 20%) were prepared. The adsorption performance effect of EG on the PCMs was observed and analyzed. The structure and thermal properties of the prepared CPCMs were characterized via scanning electron microscopy, differential scanning calorimetry, thermal conductivity measurements, and heat energy storage/release experiments. The results show that the minimum mass content of EG in the CPCMs is 7.6%. The phase-change temperature of the CPCMs is close to that of the PCMs, at around 19 °C. The latent heat of phase change is equivalent to that of the PCM at the corresponding mass content, and that of phase change with an EG mass content of 8% is 138.0 J/g. The CPCMs exhibit a large increase in thermal conductivity and a significant decrease in storage/release time as the expanded graphite mass content increases. The thermal conductivity of the CPCM with a mass content of 20% is 418.5% higher than that with a mass content of 5%. With an increase in the EG mass content in CPCMs, the heat transfer mainly transitions from phase-change heat transfer to thermal conductivity.

Role of Copper Nanoparticles in the Thermal and Mechanical Properties of Expanded Graphite-Reinforced Epoxy Hybrids.

Epoxy resin is extensively applied in the electronics and electrical fields because of its outstanding comprehensive performance. However, the low thermal conductivity (TC) limits its application in thermal interface materials. In the present work, epoxy-based hybrid composites with high TC were prepared by using expanded graphite (EG) and copper (Cu) nanoparticles as thermally conductive hybrid fillers via hot blending and compression-curing processes. Additionally, the influence of the Cu content on the thermal properties, mechanical properties, and morphology of each epoxy/EG/Cu composite was investigated. According to the results, the epoxy/EG/Cu composite showed a maximum TC of 9.74 W/(m·K) at a fixed EG content of 60 wt % owing to the addition of 10 wt % Cu. After the addition of 10 wt % Cu, the flexural strength, flexural modulus, and impact strengths of epoxy/EG/Cu composites were improved from 27.9 MPa, 9.72 GPa, and 0.81 kJ/m2 to 37.5 MPa, 10.88 GPa, and 0.91 kJ/m2, respectively. Hence, this study offers a feasible strategy for the design of epoxy hybrid composites with excellent TC that can be applied to thermal interface materials.

Experimental study of phase transition heat of composite thermal energy storage materials paraffin wax/expanded graphite

In this paper, the effect of the expanded graphite (EG) matrix on the phase transitions enthalpy of phase change material (PCM) is studied experimentally. For this purpose, the paraffin wax (PW) containing EG (up to 6.5 wt%) was explored in terms of the effective heat capacity and a diffuse phase transitions enthalpy difference over the 25–65 °С temperature range. Composite PCMs PW/EG was prepared using a new method and were inherent in high pores fill factor. The main advantage of the proposed method is preliminary vacuuming of the PW and EG with subsequent mixing and sonication under vacuum. The EG choice was based on the hypothesis that the EG matrix contributes to modifying the PW internal structure due to the PW molecules' adsorption on the EG surface during PCM cooling and solidification. Consequently, a significant change in PW/EG caloric properties vs. pure PW was observed. The EG presence in PW reverses the enthalpy hysteresis in the heating-cooling cycle vs. pure PW. The enthalpy difference during PW heating and melting in the range of 30–60 °С is higher than during its cooling and solidification: 336.2 J∙g−1 vs. 214.9 J∙g−1. On the contrary, the enthalpy difference of melting for PW/EG of 3.6 wt% in the range 30–60 °С was 171.2 J∙g−1 vs. 273.8 J∙g−1 during solidification. The obtained results are explained by the different dynamics of processes of PW melting and solidification in EG matrix pores. The presence of the 3.2–6.5 wt% of EG in PW contributes to an increase in solidification enthalpy difference in the range 30–60 °C on 27–33 % vs. pure PW. A decrease in the melting enthalpy difference for PW/EG on 44–50 % vs. pure PW was recorded in the range of 30–60 °C. In addition, thermal conductivity was measured to confirm the advantages of PW/EG as PCM. Thermal conductivity for PW/EG with EG content of 3.6 and 6.5 wt% at 25 °C was 8.9 and 9.6 times higher than for pure PW. Similarly, 8.8 and 10.9 times thermal conductivity increase was observed at 65 °C. The composite PCM containing 3.6 wt% of EG in PW obtained by developed method can be recommended as a rational composition in benefit of the thermal conductivity and caloric properties for utilization in high-performance TES systems.

Fabrication of expandable graphite and soybean oil-based synergistic modified polyurethane foam with improved thermal stability and flame retardant properties

Abstract Biomass soybean oil-based polyol rigid polyurethane foam (RPUF) was modified and prepared by expandable graphite (EG). The effects of EG on the thermal stability and flame retardant properties of soybean oil-based polyol RPUFs were investigated by thermogravimetric analysis, pyrolysis kinetic analysis, conical calorimetry and flue gas toxicity analysis. The results showed that modified RPUF (RPUF-4) with EG content of 20 wt% had the highest initial and end temperatures, the highest activation energy E, the lowest Ds (17.6), and the highest light transmittance (73.6 %). At the same time, RPUF-4 had the lowest heat release rate (10.1 and 16.5 kW/m2), the lowest total heat release (1.5 and 2.1 MJ/m2), and the lowest average toxic gas emissions. The current study indicated that RPUF-4 had better thermal stability and flame retardant performance, which provided a useful reference for subsequent biomass flame retardant modified RPUFs.

Experimental study of novel nickel foam-based composite phase change materials for a large-capacity lithium-ion power battery module

Thermal management strategies play an important role in the thermal safety of a power battery. Phase change material (PCM) cooling is considered the most competitive passive heat dissipation mode. In this paper, a novel nickel foam/paraffin (PA)/expanded graphite (EG) composite PCM (CPCM) is proposed for large-capacity prismatic lithium-ion battery modules. First, different proportions of nickel foam-based CPCMs were prepared. Second, the effects of different components of high thermally conductive additive EG on the thermal conductivity, thermal physical properties, thermal stability, and mechanical properties of the composites were studied in depth. Moreover, the fundamental reasons for the aforementioned property changes were analyzed from the microscopic point of view. The results showed that when the content of EG was 4 wt%, the thermal conductivity of the CPCMs approached the peak, which was 1.66 W/(m·K). The peak tensile strength and bending strength of the CPCMs were 2.75 and 6.59 MPa, respectively. The comprehensive analysis showed that adding 4 wt% of EG in the CPCMs was an optimum strategy. Eventually, these compound CPCMs were applied to a large-capacity prismatic lithium-ion power battery module. The experimental results demonstrated that compared with the natural air-cooling module and forced air-cooling module, the peak temperatures (Tmax) of the CPCM cooling module were decreased by 19.52% and 5.79%, and the peak temperature differences (Tmax − Tmin) were decreased by 38.15% and 35.41%, respectively. It is worth noting that even at a 1.5C high-rate uninterrupted charge/discharge cycle repeated five times, the highest temperature is always maintained below the safe temperature (55 °C), and the peak temperature difference is less than 5 °C, showing the dual advantages of the excellent temperature-controlling and temperature-equalizing abilities. The relevant outcomes will provide new ideas and theoretical value for the heat dissipation modes of large-capacity lithium-ion power batteries, ultimately promoting thermal safety performance.

Development of a Functional Cementitious Mixture with Expanded Graphite for Automated Spray Construction

Spray-based three-dimensional (3D) concrete printing is an innovative method to automatically construct structures on vertical and overhead surfaces, which contributes to less labor investment and construction time. On the other hand, expanded graphite is widely known for its high thermal and electrical conductivity as a lightweight ingredient, and thus its potential in functional cementitious materials has been gradually realized in recent years. In this study, a lightweight cementitious material containing expanded graphite has been developed specifically for spray-based 3D concrete printing with added values. Through the characterization and overall evaluation of densities, mechanical and rheological properties, and Joule-heating performance, the appropriate expanded graphite content was determined as 1% by weight of cement. Afterward, silica fume was introduced into the matrix to tailor the rheological properties of the mixtures. The subsequent spray-based printing showed that the tailored mixture had significant improvements in the building capacity and spray quality. On the other hand, it also possessed superior Joule-heating performance than the control mixture without expanded graphite. The potential engineering applications of the developed material include deicing and structural health monitoring, and the compatibility with spray-based 3D concrete printing provides extra values of higher construction efficiency and adaptivity to the structures of complex contours.

Effects of expanded graphite content on the performance of MgO‐C refractories

AbstractExpanded graphite was introduced into a MgO‐C refractory to suppress its thermal expansion and thus enhance thermal shock resistance. The refractory was prepared by mixing MgO powders (particle size = 75 μm and 1 mm), antioxidant and curing agents, flake and expanded graphite, and a novolak‐type phenolic resin at 50°C. This was followed by aging at 20°C for 24 h, compacting by uniaxial pressing, curing at 210°C for 5 h, and heat treatment at 1500°C. With an increase in expanded graphite content from 0 to 4 wt.%, the bulk density decreased, apparent density remained unchanged, and apparent porosity increased. The gaps created in the vicinity of MgO particles because of this increase in apparent porosity buffered the thermal expansion of MgO. This increased resistance to thermal shock up to 1500°C. However, the increase in expanded graphite content also had a detrimental effect reflected in the decrease in fracture strength and increase in the residual strain after repeated thermal shock. This contradiction indicates that composition optimization is important for the practical performance enhancement of MgO‐C bricks. The optimum content of the expanded graphite was determined as 2 wt.%.

Evaluation and characteristic analysis of compressive strength and resistivity of EG cement conductive mortar based upon hybrid-BP neural network

A concise general equation is difficult to reflect the relationship between physical properties of conductive materials and properties of conductive mortar (CM). To handle this issue, a back propagation neural network (BPNN) model with a topology of 4–10-2 was designed, which was further optimized with the Ant colony optimization (ACO), Genetic algorithm (GA) and Particle swarm optimization (PSO) algorithms. The models intended to establish non-linear relationships among the input layer parameters, viz., expanded graphite (EG), carbon fiber (CF), slag powder (SP), and fly ash (FA) contents, and the output layer parameters including the CM’s compressive strength and resistivity. A total of 112 groups of data points were used for model development, including 80 groups of training set data, and two series of 16 data groups for verification and testing. Influence of conductive materials on compressive strength and resistivity of CM was determined with a correlation analysis. Meanwhile, the importance and total scores of different proportions were analyzed by performing a principal component analysis on the dataset. It was found that both the EG and FA content were correlated negatively with the CM’s compressive strength and resistivity. In addition, the CF and SP contents were correlated positively with the CM’s compressive strength but negatively with resistivity. The order of the conductive substances’ importance in CM’s compressive strength and resistivity was EG > CF > SP > FA, and the group B-3 was determined as the best mix ratio. The PSO-BPNN model had the highest accuracy in predicting both the CM’s compressive strength and resistivity, which can provide guidance for mix design of CM.

Thermal Performance Analysis of Composite Phase Change Material of Myristic Acid-Expanded Graphite in Spherical Thermal Energy Storage Unit

In order to improve energy storage efficiency and promote the early achievement of global carbon neutrality goals, this paper proposes a spherical thermal storage unit filled with a composite phase change material (CPCM) comprising myristic acid (MA) and expanded graphite (EG). The effects of EG content and Stefan number (Ste) on the melting performance were investigated through a combination of experiments and numerical simulations. The results show that an increase in EG content (especially for ≥4 wt.% EG) leads to a temperature profile that assumes a concentric ring shape, while the melting rate increases with an increase in both the EG mass fraction and the Ste number. Compared to pure MA, the time required to complete melting was reduced by 82.2%, 85.6%, and 88.0% at EG contents of 4 wt.%, 5 wt.%, and 6 wt.%, respectively. Notably, the Ste value has a greater effect on melting when the EG content is ≤3 wt.%. The optimal EG content in the spherical cell was determined to be 4 wt.%, and a dimensionless analysis established a general correlation between the liquid mass fraction and the Fo, Ste, and Gr numbers.

Construction of new conductive networks for expandable graphite-based cement composites via a facile heat treatment process

Electro-thermal applications of cement composites are restricted by their poor conductivity. This study expands the homogeneously distributed graphite inside the matrix via a facile heat treatment process to form new conductive networks, thus endowing the cement composites with excellent conductivity. The obtained cement composites exhibit excellent electro-thermal performance and reliable cyclic heating properties. The average surface temperature of the composite is approximately 417 °C under 20 V, with uniform heat distribution. The surface temperature of the composites can be controlled by the expanded graphite content and applied voltage. Furthermore, the obtained cement composite melts 150 g ice cubes in 12 min under 12 V, thus exhibiting excellent deicing performance. The excellent electro-thermal performance facilitates the usage of cement composite in Joule heating applications, such as indoor climate control, pavement deicing, and cooking, thus considerably broadening the applications of cement and concrete composites for a sustainable and resilient future.

Investigation of the Flame Retardant Properties of High-Strength Microcellular Flame Retardant/Polyurethane Composite Elastomers.

Flame retardants (FRs) often reduce the mechanical properties of polymer materials, and FR/microcellular polyurethane elastomer (MPUE) composite materials have not been systemically studied. Hence, we conducted this study on FR/MPUE composites by using multiple liquid FRs and/or expandable graphite (EG). Compared with liquid flame retardants, the LOI of an expandable graphite/dimethyl methylphosphonate (EG/DMMP) (3:1) combination was significantly increased (~36.1%), and the vertical combustion grade reached V-0 without a dripping phenomenon. However, the corresponding tensile strength was decreased by 17.5%. With the incorporation of EG alone, although the corresponding LOI was not a match with that of DMMP/EG, there was no droplet phenomenon. In addition, even with 15 wt% of EG, there was no significant decline in the tensile strength. Cone calorimeter test results showed that PHRR, THR, PSPR, and TSR were significantly reduced, compared to the neat MPUE, when the EG content surpassed 10 wt%. The combustion process became more stable and thus the fire risk was highly reduced. It was found that flame retardancy and mechanical properties could be well balanced by adding EG alone. Our proposed strategy for synthesizing FR/MPUE composites with excellent flame retardancy and mechanical properties was easy, effective, low-cost and universal, which could have great practical significance in expanding the potential application fields of MPUEs.

Eutectic Fatty Acids Phase Change Materials Improved with Expanded Graphite.

Low- and ultra-low-grade thermal energy have significant recycling value for energy saving and carbon footprint reduction. Efficient thermal energy storage technology based on phase change materials (PCMs) will help improve heat recovery. This study aimed to develop a composite eutectic fatty acid of lauric acid (LA) and stearic acid (SA) binary system with expanded graphite (EG). The experimental measured eutectic temperature was 31.2 °C with an LA-to-SA mass ratio of 7:3. Afterwards, 1~15 wt.% EG was composited to the eutectic acid, and the thermophysical properties of the composite PCMs were measured by differential scanning calorimetry (DSC) and transient plane source (TPS) methods. The results demonstrated that the phase transition temperature and latent heat of the composite PCMs were stable when the content of EG was more than 5%, and the thermal conductivity and thermal diffusion coefficient of the composite PCMs (10–15 wt.%) increased by 2.4–2.6 and 3.2–3.7 times compared with the pure eutectic acid, respectively. On this basis, a finned-coil-type reservoir was prepared, and an experimental study of heat storage and heat release performance was carried out. The results showed that the heat storage and heat release effects of the heat reservoir were the best when the EG ratio was 10 wt.%. The heat storage time was reduced by 20.4%, 8.1%, and 6.2% compared with the other three EG ratios, respectively; meanwhile, the heat release time was reduced by 19.3%, 6.7%, and 5.3%, respectively.

Characterization of expanded graphite-based erythritol/urea eutectic phase change material and corresponding mathematical solar heating application analysis

• Preparation of binary eutectic mixture of erythritol and urea. • Thermal property of eutectic with various expanded graphite contents was studied. • Supercooling and thermal conductivity of erythritol/urea eutectic were optimized. • Performance of solar heating system with phase change materials tank was studied. The mid-temperature phase change materials have attracted wide attention in solar energy storage. In this study, erythritol and urea binary eutectic mixture was prepared and expanded graphite was used to reduce supercooling and enhance thermal conductivity of the binary material. The supercooling of binary eutectic mixture with 3 wt% expanded graphite was 7.43 K, which was 43.03 K less than pure binary mixture (50.46 K). The thermal conductivity of composite phase change material was 2.25 W·m −1 ·K −1 , which was approximately 3.73 times higher than the pure eutectic mixture. The test of corrosion results turned out that the new-made material had lower corrosion rate to common metal materials. X-ray diffraction and Fourier transform infrared spectroscopy tests exhibited that no chemical reaction was triggered during the preparation of the proposed composite. The energy consumption of the solar heating system with the proposed composite was numerically investigated by TRNSYS software. Compared with the traditional heating mode, composite phase change materials integrated solar heating system could save 5 tons of standard coal in a heating season for a building with heating area of 1125 m 2 in Tianjin, China. Therefore, it is proposed as a promising phase change material for solar energy storage.

Preparation of flame‐retardant rigid polyurethane foam with bio‐based phosphorus‐containing polyols and expandable graphite

AbstractIn the last decades, rigid polyurethane foam has focused on increasing renewable components and enhancing flame retardancy due to sustainable development and fire safety requirements. Herein, we report a bio‐based phosphorus‐containing polyester polyol (PMCP) that is synthesized with dimethyl methylphosphonate, malic acid, citric acid, and 1,6‐hexanediol in one pot. The hydroxyl value of PMCP is 485 ~ 512 mg KOH/g. As a result, it can be used as the sole polyol in the production of RPUF. Moreover, expandable graphite (EG) was incorporated into RPUF‐PMCP20 to enhance flame retardance. The limited oxygen index of RPUF increases from 18.3% to 24.0% with the rise in DMMP moiety in PMCP. Moreover, the peak heat release rate (PHRR) significantly decreases from 264.2 to 129 kW/m2. Meanwhile, the time to ignition increases from 5 to 18 s. The flame retardant mechanism indicated that PMCP plays a dual role in the gaseous and condensed phases. The addition of EG exhibits an excellent blocking effect. The LOI increases from 22.5% to 27.3% with increasing EG content. In addition, both the PHRR and smoke release rate of RPUF are suppressed by incorporating EG.

Effect of blowing agent content on the structure and flame‐retardant properties of rigid polyurethane foam/expanded graphite composites

AbstractDriven by global environmental issues, the development of green building materials has become an immediate focus. In this work, n‐pentane was used as an environmentally friendly blowing agent to prepare flame‐retardant rigid polyurethane foam (RPUF) with the addition of expandable graphite (EG) successfully, and the effect of n‐pentane content on flame retardancy and compressive properties of RPUF/EG composites was investigated through limit oxygen index (LOI), vertical burning test (UL‐94), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and compressive properties test. SEM results show that the content of EG and n‐pentane causes a change in the cell structure of RPUF. The change of the n‐pentane content has also an obvious effect on the thermal stability, flame retardancy, and specific compressive strength of RPUF/EG composites. In addition, the cell structure of RPUF matrix has an obvious influence on the distribution of EG in the composites, which indirectly affects the flame‐retardant efficiency of EG. This research explores the conditions for the application of environmentally friendly RPUF and expands its application prospects.

Preparation and Performance Analysis of Form-Stable Composite Phase Change Materials with Different EG Particle Sizes and Mass Fractions for Thermal Energy Storage.

The low thermal conductivity and leakage of paraffin (PA) limit its wide application in thermal energy storage. In this study, a series of form-stable composite phase change materials (CPCMs) composed of PA, olefin block copolymer (OBC), and expanded graphite (EG) with different particle sizes (50 mesh, 100 mesh, and 200 mesh) and mass fractions are prepared by melt blending. OBC as a support material could reduce PA leakage during melting, and EG as a thermally conductive filler can improve the thermal performance of PCMs. The microstructure characteristics and chemical and thermal properties of prepared CPCMs are tested and analyzed. The results show that PA/OBC and EG have good compatibility, and there is no chemical reaction with each other to generate new substances. Thermal conductivity can be significantly improved by adding EG, and it is greatly enhanced with the increase in EG particle size at the same EG mass fraction. Simultaneously, the addition of EG increased the melting temperature of CPCMs and decreased the solidification temperature as well; meanwhile, the values of melting temperature and solidification are also reversed for CPCMs compared to PA/OBC. There is an optimal content of EG to balance the thermal conductivity and heat storage capacity for CPCMs. The addition of OBC can provide a stable geometric construction, and the leakage will be further improved with the increase in EG content. Finally, the melting time of CPCMs containing EG-50, EG-100, and EG-200 with 4 wt % EG is shortened by 52.9, 41.1, and 37.5%, respectively, compared with PCMs without EG in the heat storage and release experiments. Also, the CPCMs with EG-50 have better thermal performance compared with the CPCMs of EG-100 and EG-200.

Construction of highly efficient heat conduction channels within expanded graphite/paraffin phase change composites and their thermophysical properties

Paraffin waxes (PW) are organic phase change materials (PCMs) that can be potentially applied for the storage/release of low-temperature latent heat and thermal management. However, they have serious liquid leakage and poor thermal conductivity, which greatly restrict their practical application. Although numerous studies have been conducted to address these problems, it is challenging to achieve phase change composites (PCCs) that are characterized by high thermal conductivity and excellent phase change behavior. Herein, we put forward a novel strategy for preparing expanded graphite (EG)/PW binary PCCs with EG loading varying in the range of 10–40 wt%. The method is developed by constructing graphite sheets with high orientation inside the PCCs following compression induction. The highly oriented graphite sheets provide channels for highly efficient heat transfer, which significantly improves the thermal conductivity of the resulting EG/PW PCCs. The in-plane thermal conductivities of the EG/PW PCCs are in the range of 10.7–49.7 W m−1 K−1 under 10–40 wt% EG loading conditions, much larger than those of the previously reported EG/PW PCCs with the same EG content. The EG/PW composites also exhibit excellent compatibility, uniformity, thermostability, reliability, and phase change behaviors. These remarkable properties make the EG/PW composites promising for application in thermal management and heat storage. This work provides an efficient and generic strategy for designing and constructing high-efficiency heat transfer channels within the PCCs using sheet-shaped fillers with high thermal conductivity.

Improvement of Mechanical Properties of 20CrMnTi Steel through Microstructure Modification

Microstructure modification is an effective approach to improve the mechanical properties of materials. In the present study, expanded graphite (EG) was added in a 20CrMnTi matrix to form pearlite microstructure and proeutectoid cementite after sintering. Mechanical alloying was used to obtain a fine milled mixture with a ball/powder weight ratio of 20:1. After mechanical alloying for 10 h, the milled mixtures with different EG contents were pressurelessly sintered at 1250 °C for 10 min and then hot-pressed at 1150 °C under 30 MPa for 30 min in Ar to obtain dense and modified 20CrMnTi materials. The content of EG has a profound influence on the microstructure and mechanical properties of 20CrMnTi. A high tensile strength of 1088 MPa and a high Vickers hardness of 4.7 GPa were achieved in the 1% EG-modified 20CrMnTi, which were increased by 105% and 28%, respectively, compared with the pure dense 20CrMnTi. The formed fine pearlite and small proeutectoid cementite in the modified microstructure contributed to the improved mechanical properties of 20CrMnTi.