In this study, the effect of welding heat input on the microstructure and mechanical properties of reduced-activation ferritic/martensitic steel weld metal was investigated to provide a basis for developing welding technology for this steel, which is considered a structural material for fusion reactor blankets. Autogenous bead-on-plate gas tungsten arc welding was performed with heat inputs of 0.57, 1.38, and 2.32 kJ/mm, and the microstructural evolution and mechanical properties of the weld metal were analyzed. The fraction of residual δ-ferrite in the weld metal varied depending on the welding heat input, which acted as a primary factor contributing to the reduction in weld metal strength, although it remained higher than that of the base metal. In addition, the effect of post-weld heat treatment (PWHT) at 730 °C for 1 h was evaluated. Before PWHT, the weld metal exhibited significantly higher hardness compared with the base metal. However, after PWHT, its hardness was substantially reduced, thereby minimizing the differences in hardness of the weld and the base metal.

A cold roll-bonding process using AA1050 and AA6061 sheets, in which the initial strain of AA1050 is higher than that of AA6061, was employed to fabricate an AA1050/AA6061 layered sheet. The sheet was then annealed at various temperatures ranging from 200 to 400 °C. The as-roll-bonded sheet exhibited a typical deformation structure in which the grains were elongated along the rolling direction. The evolution of the microstructure in the layered sheets varied significantly depending on the location, resulting in an inhomogeneous distribution of hardness along the thickness direction. After annealing up to 300 °C, both the AA1050 and AA6061 regions still mainly exhibited a deformed structure. Complete recrystallization occurred in the specimens annealed at temperatures above 350 °C. The hardness decreased with increasing annealing temperature in both AA1050 and AA6061, but the decrease was greater in the AA6061 region than in the AA1050 region. Resultantly, at 350 °C or higher, hardness was almost the same in all regions. The specimen annealed at 350 °C exhibited the best mechanical properties in terms of the balance between tensile strength and elongation. It is concluded that AA1050/AA6061 layered Al sheets with excellent mechanical properties can also be fabricated by CRB when AA1050 has a higher initial strain than AA6061, and subsequent annealing.

The Al-Fe-Mg-Cu-B system aluminum alloy is used for electrical wire, but is severely deformed by the multi-pass drawing process when a rod with a diameter of 12 mm is greatly reduced to 2.0 mm. This study investigated the changes in the microstructure, mechanical properties, and electrical properties of the aluminum wire during the drawing process in detail. The as-drawn aluminum alloy wire exhibited a deformation structure in which the grains were greatly elongated in the drawing direction, particularly in the specimens subjected to more than 80 % reduction in cross-sectional area (RA). For all drawn specimens, the fiber texture of the {110}<111> and {112}<111> components was mainly developed. The hardness tended to increase with increasing RA due to work hardening. In particular, when the RA increased to 97 % a great increase in hardness resulted. The specimen with an RA of 97 % showed the highest tensile strength of 288 MPa, 2.2 times higher than that of the specimen before drawing. The electrical conductivity decreased slightly with increasing RA, even in specimens with extreme increases in RA, and it remained at an average value of 56.6 %IACS.

WC–Mo₂C–Co cemented carbides were fabricated to investigate the effects of Mo₂C addition on microstructure and mechanical properties. Dual hard-phase design using WC and Mo₂C was employed to optimize the balance between hardness and toughness. Spark plasma sintering (SPS) was conducted at various temperatures after ball milling, and 1300 °C for 5 min was identified as the optimized sintering condition, achieving complete densification and phase stability. The addition of Mo₂C refined the microstructure by suppressing abnormal WC grain growth through preferential dissolution of Mo₂C into the Co binder. Hardness increased up to 1769 Hv30 due to grain refinement and solid-solution strengthening, while promoted η-phase formation and reduced fracture toughness.The 27Mo₂C composition exhibited the most balanced combination of hardness and toughness. These results demonstrate that controlled Mo₂C addition enables dual hard-phase strengthening and microstructure optimization in WC–Mo₂C–Co carbides for advanced cutting and forming applications.

The recent development of small modular reactors (SMRs) and the adoption of higher-enrichment fuels have intensified the need for advanced burnable absorbers to ensure effective reactivity control and extended fuel cycles. Among various designs, UO2 fuels with high Gd2O3 (gadolinium oxide) content provide notable benefits; in particular, they are compatible with established fabrication methods for burnable absorber fuels. However, achieving a homogeneous dispersion of Gd2O3 at high loading levels remains challenging, and the frequent occurrence of phase segregation and non-uniform microstructures can limit fuel reliability and performance. Overcoming these limitations requires an understanding of the powder characteristics and mixing behaviors during fabrication. In this study, we investigate the effects of the initial particle size and mixing method of UO2 and Gd2O3 powders on the microstructure and mixing homogeneity of high-Gd2O3-content fuels. The findings indicate that both the mixing method and the preparation state of the starting powders significantly affect the resulting microstructure and mixing uniformity.

Electrochemical treatment has a significant effect on the properties of carbon fibers (CFs). In this study, the effect of mild electric field action on the microstructure and properties of polyacrylonitrile (PAN)-based high-modulus CFs (HMCFs) and high-strength CFs (HSCFs) was investigated. Under the action of a mild electric field, CFs did not show obvious defects, but their microstructure, mechanical properties and electrical properties were affected. For HMCFs, the graphitization degree in both axial and radial directions of the fibers had a decreasing trend, the grain spacing increased, and the grain size and degree of orientation decreased, which led to a decrease in the tensile strength, tensile modulus and axial conductivity. However, for HSCFs, the pattern of change was exactly opposite to that of HMCFs. The results of this study can provide useful guidance for optimizing the production process and surface modification of CFs.

To further increase the mechanical properties of polyacrylonitrile-based carbon fibers, a multiple stretching technique was applied. Carbon fibers were multiple stretched at 2200 °C and characterizations such as SEM, Raman, XRD, and TEM were used to investigate the evolution of microstructure of carbon fibers. It was found that the grooves on the surface of carbon fibers along the fiber axis direction became more obvious and the cross-section of fibers were twisted from nearly circular to elliptical after multiple stretching. Growth and slippage of graphite microcrystals along the fiber axis direction resulted decrease in disordered structure and defects in the carbon fibers and increase in the degree of graphitization. The multiple stretching effectively enhanced the length-to-width ratio of microcrystals. An increase of 75 GPa in tensile modulus and a retention rate of 0.95 in tensile strength were realized for carbon fibers multiple stretched at 2200 °C.

This study investigated the effect of the hatch spacing parameter on the microstructure and mechanical properties of SA508 Gr.3 steel manufactured by laser powder bed fusion (L-PBF) for a nuclear pressure vessel. Materials were prepared with varying hatch spacing (0.04 mm [H4] and 0.06 mm [H6]). The H4 exhibited finer and more uniformly distributed grains, while the H6 showed less porosity and a lower defect fraction. The yield strength of the H4 material was higher than that of the H6 material, but there was a smaller difference between the materials in tensile strength. The measured elongation was 5.65% for the H4 material and 10.41% for the H6 material, showing a significantly higher value for H6. An explanation for this is that although the H4 material had a microstructure of small and uniform grains, it contained larger and more numerous pore defects than the H6 material, facilitating stress concentration and the initiation of microcracks.

본 연구는 꼬막 패각 잔골재와 PP 폐어망 섬유를 혼입한 자원순환 콘크리트의 역학적 성능과 계면 변화 영역에서의 미세구조 특성 을 분석하였다. 패각 잔골재와 폐어망 섬유를 적절한 방법으로 전처리하고 자원화를 고려하여 3D 프린팅 콘크리트 배합을 선정해 콘 크리트 시편을 제작하였다. 제작된 시편은 KS L ISO 679 규정에 따라 압축강도와 휨강도를 측정하였고, BSE 모드를 이용한 SEM 이 미지 촬영을 통해 미세구조를 분석하였다. SEM 이미지는 히스토그램 및 형상 기반 상 분리 방법, 그리고 계면 변화 영역의 픽셀값 차 이를 활용하여 이미지를 분리하고 미세구조를 분석하였다. 역학적 성능을 확인하기 위해 PP 섬유를 0.0%, 0.5%, 1.0vol.% 혼입한 시 편의 압축강도와 휨강도를 측정한 결과, PP 섬유 0.5vol.% 혼입 시 섬유 브릿징 효과로 인해 가장 높은 압축 및 휨강도가 나타났다. SEM 이미지 분석 결과, 일반 잔골재와 바인더 계면보다 패각 잔골재와 바인더 계면에서 더 큰 직경의 공극이 관찰되었으며, PP 섬유 와 바인더 계면에서는 상대적으로 작은 공극이 형성됨을 확인하였다. 이를 바탕으로 미세구조 분석 결과와 역학적 성능 간의 상관관 계를 규명하였다.

A cold roll-bonding (CRB) process is applied to fabricate an AA1050/AA5052 layered sheet. In the process, commercial AA1050 and AA5052 sheets of 1 mm thickness, 40 mm width and 300 mm length are stacked onto each other, and then reduced to a thickness of 0.5 mm through a 2-pass cold rolling process without lubricant. The roll-bonded AA1050/AA5052 layered sheet is then annealed for 1 h at various temperatures from 200 to 400 °C. The specimens annealed at temperatures below 250 °C showed a typical deformation structure in which the grains were elongated along the rolling direction. However, the specimens annealed at temperatures higher than 300 °C exhibited recrystallization structures in both the AA1050 and AA5052 regions. All the roll-bonded and subsequently annealed specimens showed an inhomogeneous distribution of hardness in the thickness direction, in which the hardness in the AA5052 regions was higher than that in the AA1050 regions. As the annealing temperature increased, the tensile and yield strengths decreased and the elongation increased gradually. The mechanical properties were compared to those of commercial AA1050 and AA5052 materials and CRBed AA5052-2L materials from a previous study.

This study investigated the optimal process conditions and mechanical properties of Cu-10Sn alloys produced by the powder bed fusion (PBF) method. The optimal PBF conditions were explored by producing samples with various laser scanning speeds and laser power. It was found that under optimized conditions, samples with a density close to the theoretical density could be fabricated using PBF without any serious defects. The microstructure and mechanical properties of samples produced under optimized conditions were investigated and compared with a commercial alloy produced by the conventional method. The hardness, maximum tensile strength, and elongation of the samples were significantly higher than those of the commercially available cast alloy with the same chemical composition. Based on these results, it is expected to be possible to use the PBF technique to manufacture Cu-10Sn products with complex 3D shapes that could not be made using the conventional manufacturing method.

We investigated the microstructure of an FeCrMnNiCo alloy fabricated by spark plasma sintering under different sintering temperatures (1000–1100°C) and times (1–600 s). All sintered alloys consisted of a single face-centered cubic phase. As the sintering time or temperature increased, the grains of the sintered alloys became partially coarse. The formation of Cr7C3 carbide occurred on the surface of the sintered alloys due to carbon diffusion from the graphite crucible. The depth of the layer containing Cr7C3 carbides increased to ~110 μm under severe sintering conditions (1100°C, 60 s). A molten zone was observed on the surface of the alloys sintered at higher temperatures (>1060°C) due to severe carbon diffusion that reduced the melting point of the alloy. The porosity of the sintered alloys decreased with increasing time at 1000°C, but increased at higher temperatures above 1060°C due to melting-induced porosity formation.

To reduce production cost and inhibit the aggregation of graphene, graphene oxide and copper nitrate solution were used as raw materials in the paper. Cu particles were introduced to the graphene nanosheets by in-situ chemical reduction method in the hydrazine hydrate and sodium hydroxide solution, and the copper matrix composite reinforced with Cu-doped graphene nanosheets were fabricated by powder metallurgy. The synthesized Cu-doped graphene was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The relative density, hardness, electrical conductivity and tensile strength of the copper matrix composite reinforced with Cudoped graphene were measured as well. The results show that copper ions and graphene oxide can be effectively reduced by hydrazine hydrate simultaneously. Most of oxygen functional groups on the Cu-doped graphene sheets can be removed dramatically, and Cu-doped graphene inhibit the graphene aggregation effectively. Within the experimental range, the copper matrix composites have good comprehensive properties with 0.5 wt% Cu-doped graphene. The tensile strength and hardness are 221 MPa and 81.6 HV, respectively, corresponding to an increase of 23% and 59% compared to that of pure Cu, and the electrical conductivity reaches up to 93.96% IACS. However, excessive addition of Cu-doped graphene is not beneficial for the improvement on the hardness and electrical conductivity of copper matrix composite.

Carbon fibers of polyacrylonitrile (PAN) type were coated with nickel nanoparticles using a chemical reduction method in alkaline hydrazine bath. The carbon fibers were firstly heated at 400 °C and then chemically treated in hydrochloric acid followed by nitric acid to clean, remove any foreign particles and functionalized its graphitic surfaces by introducing some functional groups. The functionalized carbon fibers were coated with nickel to produce 10 wt% Cf/Ni nanocomposites. The uncoated heat treated and the nickel coated carbon fibers were investigated by SEM, EDS, FTIR and XRD to characterize the particle size, morphology, chemical composition and the crystal structure of the investigated materials. The nickel nanoparticles were successfully deposited as homogeneous layer on the surface of the functionalized carbon fibers. Also, the deposited nickel nanoparticles have quazi-spherical shape and 128–225 nm median particle size. The untreated and the heat treated as well as the 10 wt% Cf/Ni nanocomposite particles were further reinforced in ethylene vinyl acetate (EVA) polymer separately by melt blending technique to prepare 0.5 wt% Cf-EVA polymer matrix stretchable conductive composites. The microstructures of the prepared polymer composites were investigated using optical microscope. The carbon fibers as well as the nickel coated one were homogenously distributed in the polymer matrix. The obtained samples were analyzed by TGA. The addition of the nickel coated carbon fibers to the EVA was improved the thermal stability by increasing the thermal decomposition temperature Tmax1 and Tmax2. The electrical and the mechanical properties of the obtained 10 wt% Cf/Ni nanocomposites as well as the 0.5 wt% Cf-EVA stretchable conductive composites were evaluated by measuring its thermal stability by thermogravimetric analysis (TGA), electrical resistivity by four probe method and tensile properties. The electrical resistivity of the fibers was decreased by coating with nickel and the 10 wt% Cf/Ni nanocomposites has lower resistivity than the carbon fibers itself. Also, the electrical resistivity of the neat EVA is decreased from 3.2 × 1010 to 1.4 × 104 Ω cm in case of the reinforced 0.5 wt% Cf/Ni-EVA polymer composite. However, the ultimate elongation and the Young’s modulus of the neat EVA polymer was increased by reinforcing with carbon fibers and its nickel composite.

In this study, the aromatic carbon content of epoxy resin (EP) increased via carbon tar pitch (CTP) modification, and the CTP occurred self-polymerization reaction. The carboxyl and hydroxyl groups of CTP and the hydroxyl and carboxyl groups of EP occurred chemical cross-linking reaction. CTP and graphitization treatment promoted EP CF carbon crystal growth. The graphitization degree of pure EP CF and 40 wt% CTP modified EP CF are 8.42% and 44.21%, respectively. With the increase CTP content, the cell size, ligament junction and density of graphitization modified EP CF gradually increased, while the number of pores and cells gradually decreased. The cell size, ligament junction size and density of 40 wt% CTP modified graphitization EP CF increased to 1200 μm, 280 μm and 0.5033 g/cm3, respectively. EP CF exhibits entangling carbon ribbon and isotropic amorphous carbon. The 40 wt% CTP modified EP CF is composed of evenly distributed amorphous resin carbon and graphite domain CTP carbon. The graphitization modified EP CF improved electrical conductivity, and the electrical conductivity of 40 wt% CTP modified EP CF is 126.6 S/m. The compressive strength can be decided by EP carbon strength and its char yield, and graphitization 40 wt% CTP modified EP CF reached 4.9 MPa. This study provides some basis for preparation and application of CTP modified EP CF.

This study investigated the effects of revolution speed and ball size in planetary milling on the microstructure and dehydrogenation behavior of TiH2 powder. The particle size analysis showed that the large particles present in the raw powder were effectively refined as the revolution speed increased, and when milled at 500 rpm, the median particle size was 1.47 μm. Milling with a mixture of balls of two or three sizes was more effective in refining the raw powder than milling with balls of a single size. A mixture of 3 mm and 5 mm diameter balls was the optimal condition for particle refinement, and the measured median particle size was 0.71 μm. The dependence of particle size on revolution speed and ball size was explained by changes in input energy and the number of contact points of the balls. In the milled powder, the endothermic peak measured using differential thermal analysis was observed at a relatively low temperature. This finding was interpreted as the activation of a dehydrogenation reaction, mainly due to the increase in the specific surface area and the concentration of lattice defects.

In contrast to conventional silk fibroin, spider silk's potential as a scaffold material for tissue engineering is examined in this work. The remarkable qualities of spider silk are being researched for use in making films for tissue regeneration. In comparison to silk fibroin films, the study's analysis of orb-web spider Trichonephila clavata films highlights their improved cell adhesion and nanofibrous network structure. Tests for solubility substantiate the durability of spider silk films, while in vitro investigations demonstrate low cytotoxicity and enhance cellular viability. The conclusion highlights the exceptional properties of spider silk, which make it a viable option for tissue engineering applications and a step forward for in vitro cell culture and regenerative bioengineering.

Transmission electron microscopy was used to examine the microscopic structural features and myofibril organization of cardiac muscle cells in the orb-web spider T. clavata. There are many myofibrils, many mitochondria, a large sarcoplasmic reticulum, and transverse tubules (T-tubules) in the muscle fibers, even if the myofibril striations may not be as noticeable as in skeletal muscles. Because of their consistent striations, sarcomeres are characterized by Z-lines that are 2.0 μm on average in length and do not clearly distinguish between the A- and I-bands. A single T-tubule paired with a terminal cisterna of the sarcoplasmic reticulum constitutes a dyadic junction, which is primarily located at the A-I level of sarcomeres. Cells are joined by intercalated discs, which create several linkages via specialized junctions such as desmosomes, gap junctions, and fascia adherens—all of which are essential for heart function. Our results with transmission electron microscopy (TEM) clearly show that the contraction of the spider's heart muscle is neurogenically controlled, since each fiber is innervated by a motor neuron branch via neuromuscular junctions. These results highlight the neurogenic process controlling spiders' cardiac muscle contractions and advance our knowledge of the peculiar cardiac muscle structure of these animals.

Silk fibroin (SF) from silkworms has special qualities, and these qualities have drawn a lot of interest lately in SF-based hydrogels for a range of biological applications. However, because there is a dearth of naïve silk materials to collect and prepare, research on the SF-based hydrogels isolated from spider silks has been rather limited. Thus, this study compared the microstructural properties of silk fibroin (SF) hydrogel scaffold, which was taken from the cocoon of the insect silkworm Bombyx mori, with those of hydrogel scaffolds derived from two types of woven silk glands in the orb-web spider Trichonephila clavata: the major ampullate gland (MAG) and the tubuliform gland (TG). The SF hydrogel, which is stabilized by connected SF fibers, has a loose top structure, high porosity, and translucency, according to our FESEM investigation. While the TG hydrogel showed greater porosity, ridge-like or wall-like structures, and stable biocapacity generated by physical cross-linking, the MAG hydrogel showed even higher porosity, elongated fibrous structures, and superior mechanical properties. It is anticipated that the unique microstructural properties of MAG and TG hydrogels will be advantageous when choosing customized substrates to support particular cell types for tissue engineering and regenerative medicine applications.