CO₂ methanation over Ni-based catalysts was studied under conditions simulating steelworks off-gas with trace H₂S. Sulfur in the feed gas deactivated the catalyst, but high-pressure operation suppressed the deactivation. Highly crystalline Ni formed under these conditions may enhance sulfur tolerance. High-temperature calcination also improved crystallinity and durability.

This study explores a method for the synthesis of formic acid from CO₂ through the utilization of biomass-derived bio-oil, specifically focusing on leveraging levoglucosan (LGA) as a key intermediate. Formic acid has the potential to be a feedstock for the synthesis of oxalic acid, a key chemical compound in an iron-making method proposed by the authors. The research investigates the pyrolysis of lignocellulosic biomass, emphasizing the effects of oxalic acid washing on the yield of LGA and its content in bio-oil. By employing a fixed-bed pyrolyzer, the study demonstrates a significant increase in LGA yield when using oxalic acid-treated biomass compared to untreated sample. The pyrolysis with a fluidized-bed pyrolyzer successfully prepared bio-oil rich in LGA during 30 min of continuous operation. Additionally, the produced bio-oil is applied in a CO₂ alkaline hydrothermal conversion process to synthesize formic acid, highlighting the potential of LGA as both a reducing agent and a formic acid precursor. The findings indicate that the LGA-rich bio-oil not only enhances the formic acid yield but also exhibits superior performance compared to conventional reducing agents such as glucose. The study also considers challenges associated with improving CO₂ conversion efficiency, suggesting that the application of bio-oil could be a promising pathway for sustainable CO₂ utilization. The results pave the way for further optimization of bio-oil production and its integration into carbon capture and utilization (CCU) processes.

This study systematically investigates the catalytic performance of Ni-supported metal oxide catalysts in CO₂ methanation, focusing on seven supports: ZrO₂, α-Al₂O₃, γ-Al₂O₃, MgO, TiO₂, ZnO, and CeO₂. In response to carbon utilization demands, CO₂ methanation, converting CO₂ and H₂ into synthetic methane, provides a promising route for renewable fuel production and energy storage.

An integrated approach of experimental evaluation and quantum chemical calculations was employed to examine adsorption stabilities of key intermediates (e.g., OH, OCHO, and other species) and to correlate these findings with catalytic activity. Experimental results indicated that ZrO₂ achieved the highest CO₂ conversion (49.2%) and CH₄ selectivity (73.5%), followed by α-Al₂O₃ (46.0%) and CeO₂ (42.9%), while MgO displayed moderate performance. In contrast, TiO₂ and ZnO were nearly inactive under the tested conditions. Computational findings confirmed these observations, demonstrating that adsorption energy and bond order are strong predictors of efficiency.

Notably, ZrO₂ and CeO₂ were predicted to stabilize multiple reaction pathways, highlighting their versatility; Computational results provided insight into α-Al₂O₃'s high activity in specific routes. By comparing single-metal-atom and twelve-metal-atom models, it was shown that smaller systems capture essential trends, thereby reducing computational requirements.

In conclusion, these results illuminate the critical role of adsorption stability in determining CO₂ methanation performance. Optimizing electronic properties and adsorption characteristics is crucial for enhancing catalytic efficiency. The combined experimental-computational analysis provides a basis for designing Ni-supported metal oxide catalysts that advance sustainable CO₂ utilization and energy solutions. These findings offer valuable guidelines for optimizing catalyst design and improving catalytic efficiency for industry.

This study investigates a passive type of thermal regulation for CO₂ methanation using catalyst pellets, comprising Ni catalysts supported on pellets composed of an Al–Cu–Si based microencapsulated phase change material (MEPCM, heat storage temp.: 519°C), with latent heat storage functions. The effects of catalyst bed configurations; a uniform type and multi-stage types on temperature profiles in the catalyst beds and CO₂ conversion were mainly investigated. Here, uniform type is only Ni/Al–Cu–Si MEPCM pellets were packed. The multi-stage types are with different mass fractions of Ni/MEPCM pellets and MEPCM pellets (no catalyst) in each stage. Compared to the uniform configuration, the multi-stage gradient configuration demonstrated an extended duration of temperature stagnation at around the heat storage temperature of the MEPCM and a reduction in the steady-state temperature at the inlet-side location. This effect can be attributed to the dilution of the catalyst bed with Al–Cu–Si MEPCM pellets, which suppressed the heat generated by the reaction and prevented excessive temperature increases. On the other hand, at the downstream temperature, the two-stage gradient and three-stage gradient configurations exhibited shorter durations of temperature stagnation and higher steady-state temperatures. In addition, the CO₂ conversion observed for the multi-stage gradient configurations were lower than that of the uniform configuration.

For reducing CO₂ emissions from blast furnace, carbon recycling blast furnace has been proposed. In carbon recycling blast furnace, reducing agents are synthesized from CO₂ by carbon recycling technology and injected into blast furnace. It has been reported that by synthesizing methane from CO₂ in the blast furnace gas and using it as a reducing agent, CO₂ emissions could be reduced by about 30% compared to conventional blast furnace. However, it has not been investigated what type of reducing agent is suitable for carbon recycling blast furnace. Therefore, this study aims to examine what reducing agents are effective for CO₂ emission reduction of carbon recycling blast furnace. First, candidate chemical species for the reducing agent of carbon recycling blast furnace were investigated and extracted. Then, the amount of carbon consumption of carbon recycling blast furnace when different candidate reducing agents are injected into carbon recycling blast furnace was evaluated by using Rist diagram analysis. The effect of blast oxygen concentration on the amount of carbon consumption were also evaluated. Based on these results, it was clarified that the amount of carbon consumption of carbon recycling blast furnace is mainly affected by the calorific value of partial combustion of reducing agent and blast oxygen concentration. It was found that by using hydrocarbons with higher calorific value of partial combustion than 4000 kJ/kg as reducing agents of carbon recycling blast furnace, carbon consumption and CO₂ emissions could be reduced by up to 40% compared to conventional blast furnace.

The high-temperature technique is fundamental but significant for a wide range of engineering and industrial fields, such as the development of functional materials, material manufacturing, and assessment. The hot-thermocouple technique is valuable because it enables us to perform in-situ observation of a high-temperature melt under rapid heating/cooling conditions of the sample. Despite its widespread use, this technique suffers from the maintenance and/or installation of new equipment because of its complexity in electrical circuits and configuration of the equipment. As of 2025, it is difficult to procure parts to maintain conventional hot-thermocouple equipment, and there are no manufacturers producing the equipment in Japan. The new system developed in this study overcomes this technical difficulty by employing LabVIEW, which is a graphical programming environment for measurement and control. The system allows us to control the temperature with high precision and a high degree of freedom. This device can be fabricated using only basic engineering knowledge by simplifying the electrical circuits of conventional hot-thermocouple devices. Test measurements demonstrated the reliability of temperature measurement using the developed system as well as its promising potential for temperature control of samples with complex patterns (e.g., sinusoidal wave with an amplitude of 50 °C and a period of 1 s). Furthermore, the production of a time-temperature-transformation diagram of the CaO–SiO₂–Li₂O system was demonstrated by in-situ observations of the sample melt using the developed system. By combining with image analysis, the timing of crystallization was determined quantitatively and mechanically, thus successfully eliminating the uncertainty caused by human analysis.

Die and molds are so-called “mother tools” and essential for mass production with good reproducibility. They require complex shapes, high surface properties and dimensional accuracy. Currently, cold working tool steel (SKD) is used for cold metal working dies. It has excellent wear resistance owing to high carbon and chromium content; however, its toughness is not necessarily high. In contrast, high speed tool steel (HSS) achieves both hardness and toughness by containing a large amount of W, Mo, V, and Co. However, the biggest drawback is the high manufacturing cost, particularly in the case of powdered HSS. If HSS is coated using additive manufacturing method on the surface of a die made from cold working tool steel, it would be possible to overcome the disadvantages of both materials and manufacture a die that combines the advantages of both materials. Therefore, the ultimate goal is coat HSS onto a cold working die. In this study, powdered high-speed tool steel (SKH40) was deposited onto an SKD61 base plate by directed energy deposition (DED). When the SKH40 powder was directly fabricated the SKD61 base plate, peeling was observed at the interface between the two materials. By gradually changing and grading the SKH40 composition ratio, the peeling at the interface was eliminated. Furthermore, it was concluded that the functionally graded materials (FGMs) deposited by DED method exhibit different microstructure and hardness than those of continuous cast material.

We systematically investigated the change in crystal orientation due to recrystallization after processing using {110}<110> single crystals as the initial orientation in the reduction range between 10–70%. The changes may be classified into two reduction cases: First, in the 10–40% reduction rate, at 10% strain, the {110}<110> grains recrystallized and gradually transitioned toward {100}<001> with increasing reduction. In particular, at 40% reduction, recrystallization was initiated from the shear bands, resulting in a dominant orientation of {100}<001> after grain growth. The {100}<001> grains recrystallized and grew from the shear bands. At a 50–70% reduction rate, the primary recrystallized orientation became {111}<211>. At 50% reduction, the {111}<211> orientations were abundant as recrystallized grains near 40% recrystallization and the orientations increased during recrystallization and grain growth. This suggests that the {111}<211> orientations formed between the shear bands as the strain rates increased, driving recrystallization and grain growth. Although the {100}<001> orientation also existed within the shear bands, both the {111}<211> and {100}<001> orientations were recrystallized. During grain growth, the {111}<211> orientation likely consumed the {100}<001> orientation.

With the growing demand for carbon capture and storage (CCS) technologies to achieve a carbon-neutral society, the low-temperature toughness of casing materials used in CO₂ injection wells has become increasingly important. This study investigates the effects of phosphorus (P) segregation at grain boundaries and prior-austenite grain size on the toughness of tempered martensitic steel API 5CT L80 Type1. Steels with different P contents and grain sizes were fabricated and evaluated through Charpy impact testing, fractography of Charpy fracture surfaces, and Auger electron spectroscopy. To comprehensively evaluate toughness-controlling factors, the Hyodo model based on the Brechet-Louchet framework was employed to calculate intergranular fracture stress. This calculation incorporated not only yield strength and grain size but also grain boundary cohesion energy estimated from the measured segregation levels of P and C. The results revealed that higher intergranular fracture stress correlates with lower ductile-to-brittle transition temperature (vTrs), demonstrating that intergranular fracture stress is an effective indicator of toughness for CCS applications. This approach enabled the combined effects of grain size and grain boundary segregation to be integrated into a single parameter.