Al-Si Alloy Powder Research Articles

Enhanced Combustion Properties of Al-Si Eutectic Alloy in Energetic Mixtures

This study investigates the feasibility of using an Al-Si eutectic alloy as a reactive fuel in energetic mixtures. Al-Si eutectic alloy powders were obtained from secondary resources and ground to a particle size of less than 100 μm. We examined these powders’ burning characteristics and thermal properties compared to pure Al powder. Results showed that the burning rate of energetic mixtures containing Al-Si eutectic alloys was 1.5 to 2.0 mm/s higher than those with pure Al. Additionally, the activation energy of pure PTFE was reduced from 81.29 kJ/mol to 61.75 kJ/mol when the Al-Si alloy was added. The formation of oxides, carbides, and fluorides in the combustion products of Al-Si-based mixtures significantly influenced their thermodynamics.

Scalable synthesis of porous silicon electrodes for lithium-ion batteries via acid etching of atomized Al–Si alloy powders

Scalable synthesis of porous silicon electrodes for lithium-ion batteries via acid etching of atomized Al–Si alloy powders

Simultaneous enhancement in mechanical and physical properties of graphene-oxide-reinforced Al matrix composites by trace-Mg-alloying strategy

This paper proposes a trace-Mg-alloying strategy to fabricate high-performance graphene oxide (GO)-reinforced Al metal matrix composites (MMC). A minute quantity (0.4 wt%) of elemental Mg was introduced in Al–Si alloy powders. Individual GO nanosheets were uniformly decorated onto the surface of the AlSiMg particle through electrostatic attractions via hetero-agglomeration. A GO network was formed at the primary boundaries of AlSiMg particles through spark plasma sintering of GO/AlSiMg mixed powders. In this process, elemental Mg reacted with the oxygen atoms within GO nanosheets, resulting in the in situ production of high-quality reduced GO. Subsequent hot extrusion disrupted the GO network owing to the metal plastic flow, causing the GO nanosheets to realign in a single direction. Consequently, the tribological behavior, tensile response, and thermal and electrical conductivities of the GO/AlSiMg composites were simultaneously enhanced. Hot extrusion led to stretching of the overlapping GO nanosheets and increased surface contact area of AlSiMg powders. Thus, the extruded samples exhibited peak electrical conductivity at 0.2 wt% GO, whereas the sintered samples demonstrated peak thermal conductivity at 0.1 wt% GO. Overall, the findings of this study highlight the potential of merging trace powder alloying and powder metallurgy techniques to create multifunctional nanocarbon/MMCs without a trade-off between mechanical and physical performance.

Macroencapsulated Al-Si phase change materials for high temperature latent thermal energy storage

This research investigated the encapsulation of Al-Si alloy phase change materials (PCMs) for efficient thermal storage at high temperature. Two strategies, the direct powder formation route and in situ powder alloying formation route, were employed successfully. In the direct powder formation route, Al-Si alloy powders were spheroidized into spheres and encapsulated within Al2O3 powder shells with the help of organic binder, which were finally sintered at high temperature, forming Al-Si@Al2O3 capsules with cavities. Isostatic pressing at 50 MPa and 200 MPa were applied to the Al-Si cores, in order to optimize the cavity size. In the in situ powder alloying formation route, Al and Si powders were used as raw materials, which could be in situ transferred to Al-Si alloy inside the capsule during the sintering formation process. With the powders as the raw materials, the final capsules obtained after sintering could provide a buffer cavity inside the capsules, which could accommodate the volumetric expansion of the PCMs during melting, thereby mitigating the potential leakage and rupture of the capsules. Investigations into the melting-solidification cycles revealed the remarkable durability of the Al-Si phase change capsules. Isostatic pressure treatment decreased internal ineffective cavities, improving the heat storage density of the capsules. The Al-12Si(Ar)-200 MPa capsule exhibited superior thermal storage performance, enduring up to 1300 cycles. The Al-12Si core had a melting enthalpy of 479 J/g, while the thermal storage density of the phase change capsule within the temperature range of 500 °C–700 °C reached 496 J/g. The results underscore the significant potential of macroencapsulated Al-Si PCM, positioning it as a promising candidate for high-temperature thermal storage applications.

Effect of pretreated Al-Si alloy powder on the microstructure and properties of Al2O3-SiC-C castables for iron runner

In ferrotitanium slag-based Al2O3-SiC-C castables, owing to the presence of more impurities in the ferrotitanium slag, the liquid content at high temperatures is extremely high, which reduces the performance of the material. In this study, the Al-Si alloy powder was hydrated, and then pretreated Al-Si alloy powder (PASAP) was used to replace Si powder and micro-silica to reduce the content of liquid in the ferrotitanium slag-based Al2O3-SiC-C castables. Compared with the sample without PASAP, the sample with 5 wt% PASAP formed numerous whiskers in situ, and the hot modulus of rupture increased by 167%. Moreover, the decrease in the liquid content of the material and the dissolution of the molten slag by Al2O3 led to an increase in the slag viscosity. The slag corrosion index of the sample with 5 wt% PASAP is decreased by 67%.

Effects of Al–Si alloy powders on mechanical properties and slag resistance of unfired magnesia refractories: In air and carbon-embedded atmospheres

Ultra-low carbon magnesia refractories used in working lining of ladle are crucial components to meet the smelting requirements for producing purity steel. However, the decreased carbon content weakened thermal shock resistance and slag resistance of refractories, resulting in the hampered practical applications. To resolve the mentioned problems, Al–Si alloy powders were introduced into unfired magnesia refractories with glucose and citric acid as binders to form combination of oxides and non-oxides, and performances of refractories were researched systematically in air and carbon-embedded atmospheres according to different service conditions, respectively. The results show that reaction mechanisms in 2 atm led to different effects on microstructure of refractories with added Al–Si alloy powders. The formation of AlN whiskers and plate-shaped MgAl2O4 and Mg2SiO4 with intersecting structure resulted in higher mechanical strength, fracture surface energy and thermal shock resistance of refractories in air atmosphere than that in carbon-embedded atmosphere. The in-situ formed ceramic phases (AlN, MgAl2O4 and Mg2SiO4) in pores led to enhanced slag resistance for refractories. Meanwhile, in carbon-embedded atmosphere, the reduced reactions of Fe2O3 in molten slag increased slag viscosity, presenting higher slag penetration resistance for refractories than that in air atmosphere. Considering the lowered compactness of refractories with excessive alloy powders by large volume expansion from the formation of ceramic phases, refractories with 3 wt% alloy powders showed high mechanical properties, thermal shock resistance and slag resistance. This study provides a reference for the development of ultra-low carbon magnesia refractories used in working lining of ladle, and the research results also indicated that the evaluation of different atmosphere conditions is important for the design of high performance refractories.

Microstructure Design of Semi-Solid Slurry for Metal Direct Writing

Metal direct writing in semi-solid slurry is an innovative technology to realize low-cost printing of load-bearing parts in contrast to laser-based additive manufacturing. However, it is challenging to achieve near net-forming of 3D parts in the current stage because of the out of controlled microstructure and hence the unstable macro extrusion of the used semi-solid slurry. Here, mixed powder remelting (MPR) is introduced to actively design the characteristics of solid phases, i.e., solid fraction, shape factor, and size distribution. Specifically, high-melting-point pure Al powder served as the dispersed solid phases in the liquid phase that transformed from Al-Si alloy powder after remelting, leading to hypoeutectic Al-Si semi-solid slurry. The effectiveness of this approach was experimentally examined and kinetically modelled, to prepare semi-solid slurry with pre-set microstructure. The improved extrusion stability of semi-solid slurry can be anticipated, and it is universal for manufacturing of metal matrix composites slurry.

Scalable Synthesis of Porous Silicon by Acid Etching of Atomized Al-Si Alloy Powder for Lithium-Ion Batteries.

Si anodes have attracted considerable attention for their potential application in next-generation lithium-ion batteries because of their high specific capacity (Li15Si4, 3579 mAh g-1) and elemental abundance. However, Si anodes have not yet been practically applied in lithium-ion batteries because the volume change associated with lithiation and delithiation degrades their capacity during cycling. Instead of considering the active material, we focused on the structural design and developed a scalable process for producing Si anodes with excellent cycle characteristics while precisely controlling the morphology. Al-Si alloy powders were prepared by gas atomization, and porous Si with a skeletal structure was prepared by leaching Al using HCl. Porous Si (p-Si12, p-Si19) prepared from Al88Si12 and Al81Si19 comprised resinous eutectic Si, and porous Si (p-Si25) prepared from Al75Si25 comprised lumpy primary Si and resinous eutectic Si. The porosity of the Si anodes varied from 63% to 76%, depending on the Si composition. The p-Si19 anode displayed the finest pore distribution (20-200 nm), excellent rate characteristics, a reversible discharge capacity of 1607 mAh g-1 after 200 cycles at a rate of 0.1 C with a Coulombic efficiency of over 97%, and high stability. The performances of the p-Si25 and p-Si19 electrodes began to decrease after 250 and 850 cycles, respectively, with a constant-charge capacity of 1000 mAh g-1 and at a rate of 0.2 C. In contrast, the p-Si12 anode maintained its discharge capacity at 1000 mAh g-1 for up to 1000 cycles without degradation. Therefore, the developed manufacturing process is expected to produce porous Si as an active material in lithium-ion batteries for high capacity and long life at an industrial scale.

Slurry preparation for semi-solid metal direct writing by a novel approach of mixed powder remelting

Extrusion-based metal direct writing is a promising metal additive manufacturing technology due to its high efficiency and low cost. However, fabricating parts with high integrity and complex geometry remains challenging. The most critical factor is the unavailable of semi-solid slurries with uniform and nearly spherical solid particles, resulting in uncontrollable extrusion and printing. Currently, mixed powder remelting (MPR) is reported to preset the features of the solid phases, including volume fraction, morphology, and size distribution. Specifically, the semi-solid slurries of hypoeutectic AlSi alloys were obtained by preheating and shearing the mixed powder composed of eutectic AlSi alloy powder and pure aluminum powder. Their microstructural characteristics and rheological behavior were investigated, demonstrating the microstructure tailoring (controllable solid fraction and size distribution, high shape factor of about 0.9) and the reduced viscosity fluctuation by a factor of 7 compared with traditional processes. MPR shows unparalleled advantages for further engineering applications of metal direct writing.

Effects of sintering techniques and parameters on microstructure and mechanical properties of Al-15Si-2,5Cu-0.5Mg compacts and Al-15Si-2,5Cu-0.5Mg/B4C composites

In this study, Al-Si compacts and Al-Si/B4C composites were produced from hypereutectic Al-Si alloy powders by cold pressing/conventional sintering and cold pressing/microwave sintering techniques. The effects of sintering temperature, sintering time and B4C particle addition on microstructural properties, density, hardness and transverse rupture strength were investigated. The phases and intermetallic compounds formed in the microstructure were determined by X-ray diffraction. Densities of the samples were measured by Archimedes’ technique. Macro hardness measurements were carried out with Brinell hardness test. Three-point bending tests were applied to the samples according to ASTM-B528–16. Elemental Al regions, master alloy (Al-Si-Cu-Mg) regions, primary Si particles and Cu- and Mg-rich secondary phases were determined in the microstructure. It was determined that the Cu- and Mg-rich secondary phases are θ(CuAl2), β(Mg2Si), γ(Al2CuMg) phases. An increase in porosity was determined in conventional sintered samples compared to green Al-Si specimens. In addition, it was observed that the amount of porosity increases, grain size and primary Si grains coarse with increasing sintering temperature in conventional sintering. The change in the amount of pores of the samples produced by microwave sintering without holding time at the sintering temperature is not as obvious as in conventional sintering. Similar microstructures were obtained in the samples at increasing sintering temperatures in microwave sintering. In the samples produced by conventional sintering, the hardness value decreased with increasing sintering temperature. Addition of 5 wt% B4C caused an increase in hardness at all sintering temperatures. The addition of 10 and 15 wt% B4C caused a decrease in hardness. In microwave sintering, the general trend in hardness change was a decrease with increasing B4C particle addition and increasing sintering time. Transverse rupture strength values close to and similar to each other in conventional sintered samples were obtained at different sintering temperatures. Transverse rupture strength values increased with the addition of 5 wt% B4C particles, and decreased with the addition of 10 and 15 wt% B4C particles.

Laser additive manufacturing of cellular structure with enhanced compressive performance inspired by Al–Si crystalline microstructure

Additive manufacturing (AM), also known as 3D printing, has greatly promoted the development of lattice structures with complex configurations. However, these lattice structures usually consist of periodically arranged nodes and struts. Here, inspired by the three-dimensional crystalline microstructure of selective laser melted (SLM) Al–Si alloy, a type of novel cellular structure with irregular nodes and struts was designed and fabricated by the SLM process with Al–Si alloy powder. The as-fabricated cellular structures were multi-scale materials from nano- to macro-scale. Electron backscatter diffraction (EBSD) analysis revealed that compared with the edge region, the central region of the struts had larger grain size, dominant (001) grain orientation, and worse toughness. Most importantly, compared with the regular lattice structures, the novel cellular structures brought about maximum 32.8% and 38.3% improvement in volumetric energy absorption Wv and specific energy absorption Ws, respectively. Furthermore, the finite element simulation was employed to reveal the stress distribution and energy absorption mechanism of cellular components during compression. Finally, the different fracture modes between the edge and central regions of the struts were investigated. The Al–Si crystalline microstructure inspired cellular structures have potential applications in biomaterials, vibration and thermal insulation.

A novel hollowed-out Si microsphere encapsulated by graphene oxide: a strong and reusable absorbent

Graphene oxide (GO) has been a promising adsorbent to remove dyes, heavy metals and other pollutants from aqueous solutions, due to its huge surface area and rich oxygenic groups. However, one of the major application challenges is the agglomeration of GO layers which greatly affect its adsorption capacity and recycle performance. In this paper, a novel hollowed-out Si microsphere encapsulated by GO layers was developed as a strong and reusable absorbent. Hollowed-out Si microsphere with a dendritic structure was obtained from micron Al–Si alloy powder via acid treatment. Then it can be encapsulated by GO layers via a hydrogen bonding interaction between oxygenic groups from GO and Si–OH/Al–OH from porous Si skeleton. The designed absorbent has excellent adsorption ability for methylene blue and heavy metal ions resulting from the large surface area and oxygen functional groups of unrolled GO sheets. Meanwhile, it shows good reusability for pollutants owing to the spread of GO sheets on the Si skeleton surface which could prevents the aggregation of GO during adsorption process.

Thermal properties of Al–Si/Al2O3 core–shell particles prepared by using steam hydration method

In this study, Al–Si/Al2O3 core–shell structured particles with a high heat storage were fabricated by keeping Al–Si alloy powder in pressurized steam for 0.5 h followed by heating at 900 °C and 1100 °C for 3 h, respectively. Both the melting and solidification point of termination for Al–Si/Al2O3 core–shell structured particles were delayed if the heating and cooling rate were too fast. The effect of heating and cooling rate on the latent heat was not obvious. Al–Si/Al2O3 core–shell structured particles prepared at 900 °C possessed relatively uniform shell and high latent heat, 292.0 J g−1, 74.8% of that of raw material. Even after 300 thermal cycles, the heat storage and heat release of this particles were still approximately 90% and 81% of that of particles before thermal cycling, while that of particles prepared at 1100 °C were 81.3% and 61.3%, respectively. The particles prepared at 900 °C has potential to be used as heat storage material or as raw material to fabricate heat storage ceramic such as ceramic honeycombs, ceramic heat storage balls and checker bricks, etc.

Ignition and explosion characteristics of micron-scale aluminum–silicon alloy powder

Aluminum–silicon (Al–Si) alloys are used in numerous applications, particularly in the automotive and electronics industries. However, because of the production of dust in the course of alloy production, the associated processes are prone to dust explosion, which can result in considerable damages. To examine the ignition and explosion characteristics of micron-scale Al–Si alloy powder, we varied the ignition energy (Ei), particle size, and dust concentration in our experiments. The effects of particle size and dust concentration on minimum ignition temperature (MIT), and Ei, particle size, and dust concentration on the explosions were studied by testing ignition and explosion parameters in a dust cloud ignition temperature testing device and a nearly spherical 20-L explosion vessel, respectively. The MIT of the Al–Si alloy powder considerably increased with increase in particle size. However, when the particle size reached a certain specific degree, the dust cloud could not be ignited. The MIT of the Al–Si alloy powder initially decreased and then increased with increase in dust concentration. In addition, a specific concentration resulted in the Al–Si alloy powder attaining the MIT, which had the highest explosion hazard. The results of the explosion test indicated that the explosion pressure (Pex) and the rate of explosion pressure rise [(dP/dt)ex] of the sample increased with increase in Ei. Similarly, the lowest Ei increased with increase in particle size; Pex of the sample alleviated as particle size increased, and Pex and (dP/dt)ex of the Al–Si alloy powder first increased and then decreased in the mass concentration range 100–900 g/m3. For four samples, the most severe explosions corresponding to the highest Pex were observed at various concentrations: 600, 700, and 800 g/m3 at an Ei of 5 kJ and 500, 600, 700, and 800 g/m3 at 9 kJ. This result indicated that the attenuation of particle size requires a reduction in the Ei, and at the same time was able to effect the decrease of the most severe explosion concentration and the minimum explosible concentrations. Thermal analysis demonstrated the accelerated oxidation stage of Al–Si alloy powder, which started at 800 °C. In addition, compared with aluminum powder of similar particle size, the continuous oxidation stage started earlier and the oxidation rate was higher. Finally, comparing Al alloy with Al powder, pure Al powder demonstrated a higher Pex in an extensive range of mass concentration, indicating its higher explosion risk.

Particle size optimization enabled high initial coulombic efficiency and cycling stability of micro-sized porous Si anode via AlSi alloy powder etching

The practical application of Si anode is still severely hindered owing to its unsatisfactory electrochemical performance, especially including poor initial Coulombic efficiency and long-term cycling stability. In this work, AlSi alloy powder was applied as precusor to prepare micro-sized porous Si. In order to better understand the effect of particle size on both morphology and electrochemical performance, the particle size of AlSi alloy powder was optimized. The results show that the average diameter of micro-sized porous Si with different particle sizes are about 5, 10, 15 μm, respectively. Besides, the initial Coulombic efficiency of micro-sized Si exhibits an increasing trend with the increase of particle size of AlSi alloy powder. The micro-sized porous Si electrode etched from AlSi alloy powder in diameter of 30 μm exhibits an initial Coulombic efficiency of 83.5% and capacity retention of 81.25% after 200 cycles at current density of 1 A g−1. The results could potentially provide a helpful guide for the scalable fabrication of micro-sized porous Si anode with high initial Coulombic efficiency and long-term cyclibility.

C2H2O4 etching of AlSi alloy Powder:an efficient and mild preparation approach for high performance micro Si anode

Metal-assisted chemical etching, such as AlSi alloy powder, has been extensively utilized in the preparation of micro-nano structure porous Si anode due to the self-template role of metal in alloy powder, low cost, and low energy consumption. In this work, we systematically investigated that the effects of etchants on the structure morphology and electrochemical performances of porous Si from etching AlSi alloy powder. C2H2O4, HCl, HNO3, H2SO4 and NaOH etchants were studied based on the principles including metallic/metalloid characteristics of Al and chemical coordination effects. The results shows that C2H2O4 can be employed as an efficient and mild alternative etchant for AlSi system instead of widely used HCl. The resulted porous Si–C2H2O4 possessed an average diameter of about 1–2 μm with numerous bicontinuous nanochannel and exhibited a specific capacity of 1063 mAh g−1 after 200 cycles at 0.5 A g−1. Futhermore, XRD, XPS, ICP and SEM characterizations reveal that the residual Al/Al2O3 show great effect on the structure morphology and the electrochemical performance of porous Si. Dominating roles of residual trace Al/Al2O3 (e.g. Si–C2H2O4) in the porous Si was also discussed to understand the structure and electrochemical performance of Si–C2H2O4. The results potentially provide a green and effective preparation approach for large-scale Si production via etching AlSi alloy powder.

Improvement of deformation capacity of gas-atomized hypereutectic Al-Si alloy powder by annealing treatment

Abstract Gas-atomized pure metal or alloy powders are widely used as raw material in the preparation of high performance materials by powder metallurgy route (compaction and sintering). However, cold compactibility of gas-atomized Al-Si alloy powder is inhibited due to the high strength as a result of the refined Si phases and the supersaturated Al matrix. The effect of annealing on improving the compactibility of Al-Si alloy powder was studied. The densification was investigated by the HECKEL compaction equation in terms of deformation capacity. Moreover, the microstructures and bending fracture surfaces of the green compacts were examined to clarify the densification behavior. The results show that a maximum relative density of 96.1% is obtained when the powder is annealed at 400 °C. The deformation capacity is significantly improved by annealing treatment due to the softening of Al matrix, precipitation of supersaturated Si phases, dissolution of needle-like eutectic phase, and spheroidization of Si phases.

Development of Hypereutectic AlSi Alloy Powder Injection Molding Feedstocks by Rheological Analysis

The comprehensive properties of a feedstock have a critical influence on the powder injection molding process. Proper feedstock with homogeneous structure, favorable flow characteristic, and moldability is the prerequisite for obtaining a final part with excellent comprehensive properties. The objective of the present work was to develop an optimal feedstock for fabrication of hypereutectic AlSi (20 wt.%) alloy parts by the powder injection molding technique. For this purpose, micron‐sized hypereutectic AlSi (20 wt.%) alloy powder was mixed with different amounts of a binder which consisted of 35 wt.% high‐density polyethylene, 62 wt.% carnauba wax, and 3 wt.% stearic acid. The binder contents of the feedstocks were in the range from 13 wt.% to 21 wt.%. The influences of binder content, shear rate, and temperature on the rheological behaviors of feedstocks have been investigated via a capillary rheometer. The feedstock with 21 wt.% binder exhibited a variable flow behavior and was culled. The rest of the feedstocks showed a pseudoplastic behavior. Comprehensive analysis of rheological parameters such as the flow behavior index, yield stress, flow activation energy, and the general moldability index, the feedstock with 17 wt.% binder exhibited the best rheological performance and favorable moldability. The molded part with 17 wt.% binder had constant density, good shape retention, and stiffness as well as homogeneous distribution of the powder and binder. After solvent debinding, the debound item showed a homogeneous porous structure which is suitable for the subsequent thermal debinding and sintering processes.

High-Rate and Long-Cycle Silicon/Porous Nitrogen-Doped Carbon Anode via a Low-Cost Facile Pre-Template-Coating Approach for Li-ion Batteries

Exploring low-cost, facile, and scalable fabrication procedure for silicon/carbon composite with excellent electrochemical performance is urgently required to promote the practical application of high-capacity silicon material for Li-ion battery anodes. Using commercial cost-effective AlSi alloy nanopowder as the silicon source, here we present a facile approach via pre-template-coating and chemical acid etching methods for synthesizing silicon/porous nitrogen-doped carbon composite with a unique core-porous shell structure. At the pre-template-coating stage, the AlSi alloy nanopowder is initially coated by carbon via the solution deposition and carbonization of PVP. The Al template is subsequently removed by acid etching, affording silicon nanoparticles wrapped by the highly conductive nitrogen-doped carbon. The escape of hydrogen gas during acid etching leads to the nitrogen-doped carbon shell with a microporous structure. The silicon/porous nitrogen-doped carbon composite with 88% Si delivers a high reversible capacity of 1730mAhg−1 (based on the total mass of the composite) after 100 cycles at a current density of 1000mAg−1 with a coulombic efficiency of approximately 100%. Moreover, the rate capability is significantly improved. With the increase in the current density from 200 to 500, 1000, 2000 and 3000mAg−1, high capacity retention values of 99.7, 97.5, 93.7 and 91.5%, respectively, are obtained. A long cycle life at a high rate is also achieved, with a notable capacity of 665mAhg−1 after 600 cycles at a high current density of 5000mAg−1. The low-cost, facile, and scalable synthesis of the approach silicon/porous nitrogen-doped carbon composite with exceptional electrochemical performance from a commercial AlSi alloy powder makes it extremely promising as a practical anode material for high-energy Li-ion batteries.

Self-standing silicon-carbon nanotube/graphene by a scalable in situ approach from low-cost Al-Si alloy powder for lithium ion batteries

Silicon/carbon (Si/C) composite shows great potential to replace graphite as lithium-ion battery (LIB) anode owing to its high theoretical capacity. Exploring low-cost scalable approach for synthesizing Si/C composites with excellent electrochemical performance is critical for practical application of Si/C anodes. In this study, we rationally applied a scalable in situ approach to produce Si-carbon nanotube (Si-CNT) composite via acid etching of commercial inexpensive micro-sized Al-Si alloy powder and CNT mixture. In the Si-CNT composite, ∼10 nm Si particles were uniformly deposited on the CNT surface. After combining with graphene sheets, a flexible self-standing Si-CNT/graphene paper was fabricated with three-dimensional (3D) sandwich-like structure. The in situ presence of CNT during acid-etching process shows remarkable two advantages: providing deposition sites for Si atoms to restrain agglomeration of Si nanoparticles after Al removal from Al-Si alloy powder, increasing the cross-layer conductivity of the paper anode to provide excellent conductive contact sites for each Si nanoparticles. When used as binder-free anode for LIBs without any further treatment, in situ addition of CNT especially plays important role to improve the initial electrochemical activity of Si nanoparticles synthesized from low-cost Al-Si alloy powder, thus resulting in about twice higher capacity than Si/G paper anode. The self-standing Si-CNT/graphene paper anode exhibited a high specific capacity of 1100 mAh g−1 even after 100 cycles at 200 mA g−1 current density with a Coulombic efficiency of >99%. It also showed remarkable rate capability improvement compared to Si/G paper without CNT. The present work demonstrates a low-cost scalable in situ approach from commercial micro-sized Al-Si alloy powder for Si-based composites with specific nanostructure. The Si-CNT/graphene paper is a promising anode candidate with high capacity and cycling stability for LIBs, especially for the flexible batteries application.