Low Expansion Coefficient Research Articles

Convenient synthesis of phthalonitrile‐containing mono‐benzoxazines with exceptional thermal stability and improved curing activity

AbstractSimple synthesis and high performance are eternal pursuit for polymers. To lower the curing temperature, lower the melt viscosity and improve the processability of high performance phthalonitrile resins, a solvent‐free method was applied to synthesize three from different phenols. Their chemical structure was confirmed by FTIR and NMR spectra, the curing behavior was investigated by DSC and rheology. It was found that the polymerization of phthalonitrile groups could be effectively promoted by benzoxazine moieties and the curing temperature of phthalonitrile groups dropped to around 240°C. Consequently, owing to the high curing reactivity, polymers obtained at relatively low curing temperature possessed high crosslinking density and extremely high thermal stability. P‐apn‐200, which was cured at 200°C, showed 5 wt% weightloss temperature (Td5) of 472°C and char yield (Yc) of 75.77% at 800°C. Moreover, the polymers obtained after curing at 280°C showed superior dimensional stability, CN‐apn‐280 showed extremely low linear expansion coefficient (CTE) of 10.7 ppm/°C. And mP‐apn‐280 showed HR capacity of 3.99 J/g‧K, peak HRR of 4.0 W/K and total HR of 0.8 kJ/g.

Preparation of low thermal expansion, transparent LAS glass-ceramics via simplified heat-treatment method

Li2O–Al2O3–SiO2 (LAS) glass-ceramics are commercially significant due to their unique microstructure and exceptional properties, including near-zero thermal expansion coefficient, making them suitable for a wide range of applications. However, the content of SiO2 and Al2O3 in the composition of LAS glass is very high, which leads to high viscosity and very difficult melting of this type of glasses. In order to reduce the melting temperature of the glass, use of relatively high Na2O in the basic glass composition allows high-quality glass to melt. Employing a simplified heat-treatment method, LAS glass-ceramics are prepared with Australian spodumene as the primary material. By exploring the effect of crystallization temperature on the structures and properties of the resulting LAS glass-ceramics, samples with excellent comprehensive properties are achieved. The prepared glass-ceramics are thoroughly characterized using DSC, XRD, FTIR, SEM, and TEM, along with assessments of their viscosity, thermal, optical, and mechanical properties. Relatively more Na2O is introduced into the glass compositions, which can lower the melting temperature of the glass to below 1600 °C. The basic glass is annealed at 700 °C for 2 h, nucleation phenomenon Nucleation phenomenon can be generated in the LAS glasses. When the microcrystalline temperature of glasses increases from 835 °C to 910 °C, the main crystalline phase of glass-ceramics changes from β-quartz solid solution to β-spodumene solid solution. The change in the main crystal phase has significantly affected the properties of glass-ceramics. When the crystallization temperature is below 860 °C, the glass-ceramics exhibit a low negative expansion coefficient (<-0.5 × 10−6 K−1), high visible light transmittance (>85 %), and excellent average flexural strength (173.3 MPa).

Preparation and Property Modulation of Multi-Grit Diamond/Aluminum Composites Based on Interfacial Strategy

The development of electronic devices has a tendency to become more complicated in structure, more integrated in function, and smaller in size. The heat flow density of components continues to escalate, which urgently requires the development of heat sink materials with high thermal conductivity and a low coefficient of expansion. Diamond/aluminum composites have become the research hotspot of thermal management materials with excellent thermophysical and mechanical properties, taking into account the advantages of light weight. In this paper, diamond/Al composites are prepared by combining aluminum as matrix and diamond reinforcement through the discharge plasma sintering (SPS) method. The micro-interfacial bonding state of diamond and aluminum is changed by adjusting the particle size of diamond, and the macroscopic morphology performance of the composites is regulated. Through this, the flexible design of diamond/Al performance can be achieved. As a result, when 150 μm diamond powder and A1-12Si powder were used for the composite, the thermal conductivity of the obtained specimens was up to 660.1 W/mK, and the coefficient of thermal expansion was 5.63 × 10−6/K, which was a good match for the semiconductor material. At the same time, the bending strength is 304.6 MPa, which can satisfy the performance requirements of heat-sinking materials in the field of electronic packaging.

DFT insights into i-MAB phase, Mo4Y2Al3B6: a potential thermal barrier coating and solar heat reducing material

We have investigated the physical properties of the i-MAB: Mo4Y2Al3B6 phase via the density functional theory (DFT) approach. The optical properties, thermal properties, and Vickers hardness of the compound Mo4Y2Al3B6 have been studied theoretically for the first time. The correctness of the fine-tuned structural parameters is confirmed by their close match with experimental results. The compound’s metallic nature is established by an analysis of its electronic band structure, which is demonstrated by the overlap of the valence and conduction bands at the Fermi level. The mechanical and dynamic stability of the compound is supported by the single crystal elastic constants and computed phonon dispersion curve. The brittleness and machinability index has been studied to predict its usefulness in any form/shape. The compound’s ability to be exfoliated into 2D nanosheets has been proven by the f-index value. The obtained Vickers hardness value indicate the materials’ softness and ease of machining, aligning with the experimental findings. The thermodynamic properties are evaluated through phonon dispersion curves, including Debye temperature, free energy, enthalpy, entropy, and specific heat capacity. The potential of Mo4Y2Al3B6 as a thermal barrier coating (TBC) material is demonstrated by its low minimum thermal conductivity (K min), low volume expansion coefficient and high melting temperature (T m ). Key optical parameters, including dielectric functions, refractive index, photoconductivity, reflectivity, absorption coefficient, and loss function, have been computed and analyzed. The reflectivity spectrum suggests that the titled compound acts as a promising coating material for mitigating solar heating.

Experimental investigation of tool feed rate and machining strategy on surface roughness in flat end milling of Nickel-Iron alloy Supra50

The Nickel-Iron alloy Supra50 is one of the commonly used materials for manufacturing aeronautical parts and is resistant to excessive thermal stress. Due to its low coefficient of expansion, this material can guarantee dimensional stability at high temperatures while also offering mechanical characteristics like those of stainless steel. However, several works in the literature demonstrate that the Nickel-Iron alloy Supra50 has low machinability due to low thermal conductivity and work hardening. These main qualities, with its magnetic characteristics, qualified it for the manufacture of components for solenoid valves in aircraft. Despite its performance, obtaining Supra50 parts by machining presents difficulties. Indeed, faced with tight dimensional and geometric tolerances, manufacturers must invest in means and methods that converge to an agreement between cost and quality that ensures the efficiency of the machining process. This research work aims to analyze the effect of machining strategies and the tool feed rate on surface roughness by using an experimental approach in a Fe-Ni-based alloy-Supra50 surfacing operation with a flat end-mill tool. This study addresses a gap in the literature, focusing on the unique challenges posed by Supra 50 machining. It was demonstrated that the feed rate strongly affects surface roughness. In other hand, it was demonstrated that the machining strategy sweep gives the minimum of arithmetic mean height of the surface (Sa), compared to other analyzed machining strategies, such as mono-directional sweep and spiral sweep. All experimental results were demonstrated in sequence with other literature works on Fe-Ni-based alloy machining.

Low-temperature cordierite ceramics with porous structure for thermal shock resistance products

This article shows the results of the study of low-temperature (1100−1150 °C) porous ceramics of cordierite composition. The technological manufacturing parameters, the features of the microstructural and phase composition of ceramics have been studied. A decrease in the sintering temperature is achieved by appending a part of components using eutectic glass of MgO–Al2O3–SiO2 pseudoternary system. The principle of reactive formation of the structure of the ceramic sample is implemented in the process of its low-temperature firing. The formation of α-cordierite occurs in the process of firing ceramics by means of intensive interaction between eutectic glass components and crystalline fillers, as well as in the result of glass crystallization. By means of the thin layers of the glassy phase, cordierite crystals form a hard base with a branched system of interconnected open pores (30.0−31.3 %). The cordierite-phase crystals, forming the structure of ceramics, have a particle size ranging from 0.2 to 0.3 μm to 1.0−2.0 μm. The specific surface area of the porous cordierite ceramics is in the range of 4.2–4.7 m2/g. The developed cordierite ceramics is characterized by its low coefficient of linear temperature expansion (1.7–2.6)·10−6 °С−1, which determines its high thermal shock resistance (1000−1150°С). The ceramics may be used as filtering elements in high-temperature filtering units, as well as catalyst carriers in the exhaust systems of combustion engines for discharging the sooty component.

EVALUATION OF CEMENT POLYMER COMPOSITES USING SPSS ANALYSIS

Cement Polymer Mixtures are made of Cement, sand, or bulk polymers are made using polymers added to improve their compressive strength, fatigue resistance, impact, and durability. Hydraulic cement polymer composites, created with modern polymer technology, are well-known for enhancing the development of composite materials and new products. This technology aims to improve both polymer cement for new construction and its use in repairing old cement. The adhesive properties of polymer cement allow for correction and bonding of both polymer-based and conventional cement. Cement-based composite materials, such as hardened cement paste, are formed by the combination of cement, water hydration, various minerals, metals, and polymeric materials. Different combinations of these materials can result in cement binders that are used for construction. Cement, a chemical substance used as a binder, sets and hardens to bind things together. It is rarely used alone and is typically combined with sand and gravel. Polymer cement is a type of cement-polymer composite where conventional cement hydrates are replaced by polymer binders or liquid resins. It is prepared by completely replacing the hydrate binders of cement with the polymer binders or liquid resins. This mixture forms a cement-polymer composite. Cement-polymer composites are durable materials that exhibit long service life and can withstand harsh environmental conditions. They are not affected by extreme temperatures, whether hot or cold, as dry concrete has a low coefficient of expansion and can accommodate moderate movements in the design. Evaluation parameters for cement include calcium oxide, magnesium oxide, silicon dioxide, aluminum oxide, sodium oxide, potassium oxide, and sulfur trioxide.

Mechanical and thermal properties of W-20Cu alloy for packaging HgCdTe IRFPA detector at cryogenic temperatures

Tungsten-copper alloy, as an electronic packaging material with excellent comprehensive performance, is widely used in the cooled packaging dewar structure of HgCdTe infrared focal plane detector. Thermodynamic properties (Coefficient of Thermal Expansion (CET), Thermal Conductivity (TC), Specific Heat Capacity (SHC)), mechanical properties and microstructure of W-20 wt% Cu(W-20Cu) are investigated in the range of 300 K ∼ 4.2 K, respectively. The quasi-static tensile tests are carried out on an electronic universal testing machine to obtain the typical stress–strain curves and mechanical properties of W-20Cu. The yield strength (YS), ultimate tensile strength (UTS), elongation and shrinkage of the specimens are measured. Besides, the Scanning Electronic Microscopy (SEM) are applied to observe the microstructure of W-20Cu alloy. The results demonstrate that W-20Cu alloy has outstanding thermal properties of high strength and hardness, high specific heat and low heat capacity and expansion coefficient. Tensile properties of the alloy significantly improve at extremely low temperature, and compared with 300 K, the YS and UTS of W-20Cu increase by 30.68 % and 11.27 % at 77 K. At 4.2 K, the YS increase by 44.49 %, and the UTS increase by 17.20 %, while the plasticity and fracture toughness have a sharp reduction from 300 K to 4.2 K. All specimens exhibit brittle fracture characteristics. With the increase of W crystals cleavage ratio and W-W continuity, the microstructure continuity and uniformity are improved. The number of plastic dimples of Cu phase decreases and the dimples become shallow slightly.

Multi-layer laser cladding analysis and high-temperature oxidative wear behavior of cast iron with a low expansion coefficient

Laser cladding is among the critical processes for repairing and strengthening cast iron parts. To further improve the application of laser cladding on cast iron and provide a feasible technical approach for its surface cladding. In this paper, different alloy powders were clad on the surface of ductile cast iron and gray cast iron, commonly used cast iron materials in engine cylinder blocks. The multi-layer claddings of various powders on the cast iron surface were analyzed, and the oxidative wear behaviors of Fe-based coatings at high temperatures were discussed. The results show that the primary defects of the cladding layer were cracks and edge warping. The average stress relationship of each coating was: ∣dσNi∣<∣dσFe∣<∣dσCo∣, and the Ni-based layer internal stress was the minimum. The internal stress was mainly caused by the difference between the physical properties of the coating and the substrate, and cladding defects were easy to occur if the internal stress was too enormous. Ni-based coating with lower cladding stress can be a transition layer to avoid defects. The average wear of Fe-based coatings at room temperature, 100, 250, 500, and 750 °C was 2.83, 1.94, 4.46, 6.43 and 9.72 mg, respectively. The wear amount was the minimum at 100 °C. Temperature rising, the oxidation of the specimens intensified, and the wear amount increased.

The Effects of Titanium Dioxide (TiO2) Content on the Dry Sliding Behaviour of AA2024 Aluminium Composite

The low density, low expansion coefficient, and strong corrosion resistance at room temperature of Aluminium alloys have made them a popular choice for engineering applications. In this study, Aluminium AA2024 alloys are prepared with different weight contents of ceramic material, titanium oxide (TiO2) nanoparticles (0%, 2.5%, 5%, and 7.5% wt.) of a particle size of 30 nm using the metal stir casting method. The hardness property and wear resistance with the effect of heat treatment are investigated using a pin-on-disc wear device for both the base alloy and the reinforced alloys. The result shows the prosperity of 5wt.% of TiO2 to attain the optimum hardness and wear resistance. Using the optimum content of TiO2 and heat treatment, the hardness and wear resistance of 5wt.% TiO2-AA2024 nanocomposite has been significantly improved after heat treatment over the unreinforced Aluminium matrix. Statistically, the hardness and wear resistance are improved by 68% and 22%, respectively. This is due to an increased number of fine precipitates besides their uniformly distributed after heat treatment. Furthermore, casting AA2024 Aluminium alloy material mainly has S (Al2CuMg) and Al3TiCu phases. The appearance of a large number of S phases causes a significant improvement in the properties of the alloy.

Study on copolymerization modification and properties of bio-based trifunctional diphenolic acid epoxy resin by CE and DPR

Diphenolic acid epoxy resin (DPAE), a new type of bio-based epoxy, exhibits many attractive performances, such as high reactivity, low expansion coefficient (CTE), high glass transition temperature (Tg) and high storage modulus. However, the dielectric constant of DPAE is not satisfied for the requirements of high frequency circuit field, which need to be further improved to expand its application in emerging area of electronic information. In this work, both dicyclopentadiene phenol epoxy resin (DPR) and cyanate ester (CE) were used to modify DPAE in order to improve its dielectric property, while keeping good heat resistance and low dimensional stability. Furthermore, the influence of curing agent types on properties of DPAE/DPR system was studied. Compared with DPAE resin, both DPAE/DPR and DPAE/CE composites exhibited higher glass transition temperature (Tg), lower dielectric constant, lower loss tangent with good compatibility between DPAE and those two resins. Moreover, CE resin exhibited better modified effect than DPR on thermal and dielectric properties of DPAE with the same addition. For example, the dielectric constant and loss tangent of DPAE/CE with 50 wt% CE were as low as 3.4 and 0.018 at 1 MHz, respectively.

Study on surface nitriding treatment of the sintered SUS430 ferritic stainless steel

Ferritic stainless steels with the advantages of high thermal conductivity, low expansion coefficient, excellent oxidation resistance, resistance to stress corrosion capacity, and low cost are widely applied. The parts are prepared by powder metallurgy with SUS430 ferritic stainless steel. Under an H2 protective atmosphere, the compactions are sintered at 1300 °C, and the density of the as-sintered sample achieves 7.4 g/cm3. Then, high-temperature solid solution nitriding treatment is carried out at 1110 °C under an N2/H2 mixed atmosphere. The nitride layers are formed on the surface of the samples. The thickness of nitride layers is about 130–150 μm, and its microhardness is 490 HV. Moreover, it suggests that gas nitriding treatment can effectively improve surface hardness and wear resistance. Still, the core matrix with ferritic microstructure maintains good plasticities and ductilities, and its hardness is about 126 HV.

Lightweight chopped carbon fiber/carbon composites with low thermal conductivity fabricated by vacuum filtration method

Lightweight carbon fiber/carbon composites (CFC) are widely used in solar silicon furnace, semiconductor long crystal furnace and other high-temperature equipment due to its superior low thermal conductivity, low expansion coefficient, high purity, good mechanical properties, and high temperature resistance. In this paper, the lightweight chopped CFC was prepared by the method of liquid phase dispersion of chopped carbon fibers-vacuum filtration-curing molding-high temperature carbonization and graphitization. The thermal conductivity of lightweight chopped CFC with different densities (0.12, 0.16 and 0.18 g/cm3) was studied, and the thermal conductivity of lightweight chopped CFC at high temperature was also studied. The results show that the thermal conductivity (1000 °C) of the chopped CFC gradually increases with the increasing density from 0.179 W/(mK) (0.12 g/cm3) to 0.190 W/(mK) (0.16 g/cm3), 0.282 W/(mK) (0.18 g/cm3), indicating that with the increasing density, the thermal conduction path of the carbon fiber increases, the thermal conductivity of the CFC material increases, and then the thermal insulation performance decreases. In addition, with the increasing temperature, the phonon vibration increases, the thermal conductivity of the CFC material also increases, and then the thermal insulation performance decreases.

In-situ crystallization of ferrochrome slag and quartz for preparing cordierite materials

Ferrochrome slag (FS) contains a large number of glass phase, which cannot be effectively transformed into crystalline phases during the reutilization for fabricating ceramic materials. In this study, cordierite with a low expansion coefficient was successfully prepared from FS and quartz. The composition and structural characteristics of FS were analyzed. The phase evolution, microstructure, coefficient of thermal expansion (CTE), and material properties were studied. With 34 wt% quartz and maximum cordierite crystal content of 75.1 wt%, the glass phase decreased from 78.7 to 12.7 wt%. The melted quartz generated silica-rich microdomains with high viscosity during heating. Subsequently, the nuclear dynamic conditions were improved to promote the formation of cordierite crystals. Appropriate sintering temperature and holding time can boost the crystallization rate of the glass phase. Further, the diffusion of silica-rich microdomains was beneficial for the formation of cordierite crystals. Finally, the optimal cordierite ceramic material was obtained at 1300 °C for 2 h with a flexural strength of 38.3 MPa and CTE of 3.01 × 10−6/°C. These studies provide an effective way of re-utilizing large volumes of FS, and suggest a new method for preparing ceramic materials using high-temperature silicate waste residues.

Разработка и исследование катушки Роговского для работы в условиях эксплуатации открытого распределительного устройства

The interest to use Rogowski coils (RC) as current sensors to design secondary systems increases due to application of microprocessor relay protection and automation devices, including those that support the reception and processing of information in a form of a digital code in the format of protocols defined in IEC61850, as well as the disadvantages of traditional electromagnetic current transformers. Despite the popularity of RC, there are many unstudied issues of their functioning under operating conditions of open switchgears of power facilities, especially when operating with modern relay protection and automation devices. The aim of the study is to analyze the effect of ambient temperature on the error of current conversion by Rogowski coils. Studies of Rogowski coils have been carried out using the experimental and industrial samples. During the research modern testing equipment has been used. The equipment is listed on the Unified Register of Measuring Equipment of the Russian Federation and has valid verification certificates. The analysis of the factors influencing the error of metrological channels has been carried out. The analysis is conducted based on traditional current transformers (CT). The factors influencing the measurement error of RC are systematized. Experimental data obtained as a result of the study of the RC conversion error in a wide temperature range are presented. It has been established that due to design solutions, it is possible to neutralize the influence of such factors as the position of the primary conductor, external electromagnetic fields, uneven winding, the number of layers of the secondary winding, and thermal expansion. The use of materials with a low coefficient of linear expansion to manufacture the core of the Rogowski coil makes it possible to obtain the metrological characteristics of the transducer that meet the requirements of normative technical documentation in a wide temperature range. Application of RC as a primary current sensor for relay protection and automation systems is a promising area that requires further comprehensive research, and specifically in the process of industrial operation.

CLEVELAND-CLIFFS 444

Abstract Cleveland-Cliffs 444 is a low carbon, low nitrogen, dual stabilized ferritic stainless steel that provides pitting and crevice corrosion resistance superior to most ferritic stainless steels and some austenitic stainless steels. It is equivalent to Type 304 austenitic stainless steel in many corrosion environments and has a lower coefficient of expansion and better thermal conductivity. Cleveland- Cliffs 444 has superior chloride stress-corrosion cracking resistance to Type 304 and Type 316 austenitic stainless steels. It is oxidation and creep resistant at elevated temperatures, making it a preferred material for the most demanding applications in automotive exhaust. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on corrosion resistance as well as forming and joining. Filing Code: SS-1355. Producer or source: Cleveland-Cliffs Inc.

セルロースナノファイバーコンポジットの高分散技術とその特徴

Cellulose Nano Fibers (CNFs) is expected to be utilized in various fields because of its attractive properties such as high strength, high rigidity, and low coefficient of linear expansion. CNFs have attracted significant attention as materials that can enhance the mechanical properties of polymers. CNFs can easily form hydrogen bonds between CNFs because of the many hydroxyl groups on the surface of a CNF. Therefore, in many cases, CNF agglomerates with diameters greater than 100 µm remain in a composite when compounded with hydrophobic polymers. Recently, we can success in preparing the dry powders of CNFs by coating of hydrophobizing agent and special drying (trial products by Sugino Machine ; 20 nm of fiber diameter, 1 and 10 µm of fiber length) . The CNFs are easily dispersed in a polypropylene (PP) matrix by melt-compounding with using a twin-screw extruder. No agglomerates of CNFs with diameters greater than 1 µm can be found in the composite by optical microscope observations and TEM observations of electron staining ultrathin section.

Research on generation of stable mid-infrared lasers with narrow linewidths based on optical feedback locking

Mid-infrared precision spectroscopy has important applications in the fields of trace gas detection and the determination of fundamental physical constants. However, due to the limited commercialization of related technologies, there is a lack of narrow linewidth laser sources or linewidth narrowing approaches in the mid-infrared region, as well as stable mid-infrared frequency standards. The most commercialized and widely used mid-infrared laser source is the quantum cascade laser (QCL). But its free-running linewidth is more than MHz scale due to the influence of laser drive current noise and temperature fluctuation. This impedes the development of precision spectroscopy in this region. In this work, we introduce a technique for generating a narrow linewidth, stable mid-infrared laser by using optical feedback frequency locking, with a high-finesse mid-infrared ultrastable Fabry-Pérot cavity as the frequency reference. The optical cavity consists of two high reflectivity mirrors separated by ultra-low expansion (ULE) material with a low temperature expansion coefficient, and its temperature is precisely controlled. And the cavity is also surrounded in a vaccum cavity made of stainless steel. All these measures ensure the cavity length and its longitudinal mode stability. By using optical feecback, a QCL is locked to the cavity, which stabilizes the laser frequency and narrows the laser linewidth. In order to improve the long-term stability of the optical feedback, an active servo is leveraged to control the feedback phase. The error signal for the servo is obtained by using the method similar to the Pound-Derver-Hall locking. In this work, we first theoretically analyze the feasibility of laser to F-P cavity frequency locking by optical feedback. We propose the laser frequency response model with a linear F-P cavity under optical feedback, and analyze the influence of the direct cavity reflection on the laser frequency. Then the experimental demonstration is conducted. Firstly, we measure the reflectivity of the cavity mirror by using cavity ring-down spectroscopy, resulting in a cavity finesse of 30200 and a cavity mode linewidth of 49.7 kHz. After that, we successfully achieve optical feedback frequency locking, and consecutive cavity transmission is observed. The error signal for the control of the optical feedback phase is used to evaluate the locking performance by converting it into the laser frequency noise. By analyzing the noise spectral density, the QCL linewidth is narrowed to 0.3 Hz on a short timescale (&lt; 10 ms). And the long-term stability is suspected to be dedicated by the temperature variation of the optical cavity, resulting in a laser frequency drift 20 kHz/12 h. The narrow linewidth stabilized mid-infrared laser source obtained with this technique is expected to serve as an effective frequency reference source for mid-infrared precision spectroscopic measurements.

Application of N-Doped Carbon–Silicon Oxycarbide Based on POSS Synthesis in Lithium-Ion Batteries

Si/C materials have attracted much attention as anode materials for lithium-ion batteries. Here, nitrogen-doped silica carbon composites with a carbon-coated structure were synthesized using poly(1-vinylimidazole) in the presence of octavinyl-silsesquioxane followed by annealing and magnesium thermal reduction processes of the polymer precursor (PPVIm). Benefiting from the moderate Si–O–C bonds, the prepared NSiOC possesses a high first discharge capacity of 1862.3 mAh·g–1 at 0.2 A·g–1 and an initial Coulombic efficiency of 70.0% at 30 °C. When the temperature rises to 60 °C, the first discharge and charge specific capacities of the synthesized anode material at 0.2 A·g–1 increase to 2103.0 and 1528.7 mAh·g–1 with an ultralong lifespan of more than 1000 cycles. Moreover, the results show that the degradation of performance during the initial phase of cycles can be ascribed to the formation of an SEI layer and insufficient electrolyte penetration. The battery maintains a steady state (nearly 600 consecutive cycles) for a long time afterward as the activation of the anode material increases, attributed to the low expansion coefficient originating from the porous structure of the carbon capping layer and silicon oxide. In addition, the electrochemical attenuation process of the electrode material with a unique inorganic silica skeleton and exceptional electrochemical performance was also investigated for the assistance of future design in high-performance electrode materials.

Powder-bed-based 3D printing with cement for sustainable casting

3D printing allows for the cost-effective fabrication of moulds and can cast complex shapes. In this study, alumina cement and fine aggregates for refractories were used as the main raw materials, and saturation was adjusted to an appropriate level to control the cement binder mixture for sand casting. For cast iron, the mould must withstand temperatures of up to 1400 °C and must exhibit sufficient strength, gas permeability, and thermochemical durability at high temperatures. To accomplish these requirements, 3D printing powder was prepared by adjusting the ratio of fine aggregate (D50: 30 μm) and an even finer cement component (D50: 4 μm). To improve the moulding quality, a green body was used to optimise the cement admixtures to increase the strength, and the saturation level of the 3D printer was adjusted for dimensional accuracy. The high-temperature durability of the mould was evaluated by measuring its strength after heat treatment, using Simultaneous Thermal Analysis (TG-DSC), and through dimensional stability assessment. In addition, the pores of the specimens were analysed through microscale X-ray tomography. The surface resolution and tolerance of the final casting were determined by a 3D image roughness test using a surface roughness scanner. The cement exhibited the shortest curing time and the highest strength when the mass ratio of CA (CaO·Al2O3) to C12A7 (12CaO·7Al2O3) was 8:2. The final mixing mass ratio of cement to the fine aggregate was 8:2, which was determined based on the relationship between flowability and powder bed surface quality. The results proved the high-temperature thermal stability of the 3D-printed mould, which showed a total mass reduction of less than 3% and a low coefficient of linear expansion up to 1300 °C. Consequently, the suitability of the 3D-printed moulded body, composed of casting sand with cement as a binder, for casting at temperatures >1400 °C was demonstrated. Additionally, the final printed porous mould de-powdered easily, and its recyclability was verified by strength testing various mass ratios of fresh and recycled powder. Therefore, through optimisation of the material combinations and adjustment of the 3D printing process parameters, optimal gas permeability and moulding resolution could be achieved without any casting defect, while maintaining handling strength. The findings of this study demonstrate the potential of expanding the scope of powder-bed-based 3D printing of cement material to the casting market.