{"title":"Curvature of free-standing polycrystalline SiC thick films grown by CVD: On the origin of the residual stress gradient","authors":"Yann Gallou , Alexandre Potier , Didier Chaussende","doi":"10.1016/j.mtla.2025.102350","DOIUrl":"10.1016/j.mtla.2025.102350","url":null,"abstract":"<div><div>Polycrystalline SiC can serve as a receiver substrate for the fabrication of engineered SiC wafers for power-electronics devices. These substrates must be as flat as possible for further processing. They can be fabricated by chemical vapor deposition (CVD) on a sacrificial substrate, which is then removed leaving a thick free-standing SiC film. When deposited by CVD, a residual intrinsic stress gradient develops through thickness of the film and results in the curvature of the free-standing film. In this study, we show that two mechanisms are responsible for the occurrence of such an intrinsic stress gradient. The first is due to a change of grain size through the film's thickness that in turn leads to a change of intrinsic stress during growth. The second mechanism is attributed to the continuous relaxation of the film during growth. Although a constant grain size through thickness can be achieved with appropriate process conditions to minimize the intrinsic stress gradient, the second mechanism occurs for any microstructure. Therefore, the intrinsic stress gradient and the resulting curvature of the free-standing films is difficult to avoid though it can be minimized through pertinent choices of growth conditions.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102350"},"PeriodicalIF":3.0,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Low-temperature bonding of HCl-dipped Ge substrate with diamond heat-spreader through atomically thin layer","authors":"Yuki Minowa , Takashi Matsumae , Yuichi Kurashima , Hideki Takagi , Masanori Hayase","doi":"10.1016/j.mtla.2025.102369","DOIUrl":"10.1016/j.mtla.2025.102369","url":null,"abstract":"<div><div>Although Germanium devices have attracted attention for post-silicon device applications, they suffer from heat dissipation problems that hinder miniaturization. This study demonstrates the low-temperature and vacuum-free bonding of a germanium substrate with a diamond heat spreader, which has the highest thermal conductivity among solid materials. For efficient heat dissipation, we designed a bonding process at 200 °C using a reduction pre-bonding treatment instead of conventional oxidation. The process suppresses the formation of a germanium oxide layer at the bonding interface. This study demonstrates that germanium and diamond substrates are bonded through a 1.6-nm-thick amorphous intermediate layer. The shear stress reached 9.43 MPa, satisfying the MIL-STD-883E standard for microelectronics. As the germanium substrate can form atomic bonds with thermally conductive materials through a thin interfacial layer, it is expected that the bonding process of the HCl-dipped Ge device can contribute to future high-frequency devices.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102369"},"PeriodicalIF":3.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143419595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MaterialiaPub Date : 2025-02-07DOI: 10.1016/j.mtla.2025.102367
R. Basumatary , P. Kalita , H. Bailung , R. Brahma
{"title":"Facile synthesis of CeO2 nanoparticles through plasma-liquid interaction","authors":"R. Basumatary , P. Kalita , H. Bailung , R. Brahma","doi":"10.1016/j.mtla.2025.102367","DOIUrl":"10.1016/j.mtla.2025.102367","url":null,"abstract":"<div><div>In this study, a facile and energy-efficient technique known as plasma-liquid interaction is employed for crystal growth, defect engineering, and band gap tuning. Using this novel procedure that minimizes the use of chemicals, cubic fluorite CeO<sub>2</sub> nanoparticles are produced. The cubic fluorite structure of the prepared nanoparticles is confirmed by the Rietveld refinement method of XRD patterns. The further crystallization of cubic CeO<sub>2</sub> nanoparticles (CeO<sub>2</sub>@300) is observed due to heat treatment following plasma interactions. However, prolonged plasma treatment led to the formation of crystallinity with the generation of oxygen-related vacancies in the host lattice. Post-heat treatment of the materials resulted in increased crystallinity and reduction in vacancies within the host matrix, as confirmed by the vacancy concentration calculations derived from XRD data and the variations of Raman absorption band intensity at 1047.24 cm<sup>−1</sup>. X-ray photoelectron spectroscopy analysis of the CeO<sub>2</sub>@RT sample reveals the presence of the Ce<sup>3+</sup> ions, indicating the existence of vacancies. TEM analysis showed a good agreement with XRD analysis, revealing a polycrystalline in nature with the particle size distribution ranging from 3 nm to 10 nm. The calculated vacancy concentration indicated a higher vacancy concentration in the CeO<sub>2</sub>@RT sample, which is further confirmed by Raman spectral analysis. The characteristic vibrations of the Ce-O functional groups are identified using FTIR at absorption bands ranging from 814 cm<sup>−1</sup> to 530 cm<sup>−1</sup>, supporting the cubic fluorite structure of the CeO<sub>2</sub> nanoparticles. The band gap energy and defect energy, calculated from the UV–vis spectrum, reveal a lower band gap energy with higher defect energy for CeO<sub>2</sub>@RT sample, and higher band gap energy with lower defect energy for CeO<sub>2</sub>@300, making these material suitable for optoelectronic devices.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102367"},"PeriodicalIF":3.0,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143419598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MaterialiaPub Date : 2025-02-06DOI: 10.1016/j.mtla.2025.102365
Mohammad Rezayat , Miguel Morales , Esmaeil Ghadiri Zahrani , Mahmoud Moradi , Bahman Azarhoushang , Antonio Mateo
{"title":"Effect of repetition passes in the laser surface texturing of AISI 301LN steel on the anticorrosion properties in molten carbonate salts","authors":"Mohammad Rezayat , Miguel Morales , Esmaeil Ghadiri Zahrani , Mahmoud Moradi , Bahman Azarhoushang , Antonio Mateo","doi":"10.1016/j.mtla.2025.102365","DOIUrl":"10.1016/j.mtla.2025.102365","url":null,"abstract":"<div><div>Laser Surface Texturing (LST) has recently emerged as a corrosion mitigation strategy for materials in contact with high-temperature molten salts used in the next-generation Concentrated Solar Power (CSP) technology. Some issues related to the LST parameters, which may affect the corrosion resistance, have not been addressed yet. Therefore, the present work is focused on the effect of laser input density and pass repetitions for improving the corrosion resistance in molten carbonate salts of AISI 301LN stainless steel. The textured surface produced by a nanosecond laser and the oxide scales formed during subsequent corrosion tests in a molten salt mixture of Li<sub>2</sub>CO<sub>3<img></sub>Na<sub>2</sub>CO<sub>3</sub>-K<sub>2</sub>CO<sub>3</sub> at 600 °C were analysed by complementary analytical and microscopy techniques. The results showed that the treated-surface samples at high laser power presented a strong decrease in corrosion rate, as compared with the as-received sample. This is attributed to the formation of a thicker and denser protective oxide scale. However, high laser power increased the susceptibility to corrosion at the heat-affected zone (HAZ). It could be effectively prevented with the accumulation of laser repetition passes, offering a new potential approach to maximize the enhancement of corrosion resistance using LST in the design of components for next-generation CSP plants.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102365"},"PeriodicalIF":3.0,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MaterialiaPub Date : 2025-02-05DOI: 10.1016/j.mtla.2025.102355
Abhishek Arya, Muhammad Nabeel, A.B. Phillion
{"title":"In situ CLSM observation of Austenite microstructural evolution during hot deformation","authors":"Abhishek Arya, Muhammad Nabeel, A.B. Phillion","doi":"10.1016/j.mtla.2025.102355","DOIUrl":"10.1016/j.mtla.2025.102355","url":null,"abstract":"<div><div>In-situ observations of microstructure evolution during the thermomechanical processing of low-carbon steel have been carried out using a high-temperature tensile testing system (HiTTS) integrated with a confocal laser scanning microscope (CLSM). Experiments were conducted within the temperature range between 800 to 1200 °C, and employing a strain rate of 0.001<!--> <!-->s<sup>−1</sup> to analyze the evolution of austenite microstructure at different temperatures and to identify the deformation and restoration mechanisms. The findings suggest that at temperatures below 900 °C, planar slip is the dominant deformation mechanism, and slip transfer is more favorable at twin boundaries than at grain boundaries. On the other hand, dynamic recrystallization (DRX) is identified as the primary restoration mechanism above 900 °C. The study identifies various nucleation sites for DRX grains, with triple junctions and grain boundaries serving as the nucleation sites at 900 °C. As the temperature increases to 1000 °C and above, new nucleation sites, such as inside annealing twin boundaries and free twin ends, are observed. The microstructure results suggest that the morphology of the twin boundary changes and loses its character during deformation. The role of annealing twin boundaries on DRX and bulging mechanisms associated with the various nucleation sites are discussed in great detail. Finally, the operational details, including temperature variations along the gauge length and thermal profile adjustments, including overshooting and undershooting and high-temperature surface reactions such as oxidation, decarburization, and evaporation, are meticulously examined.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102355"},"PeriodicalIF":3.0,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MaterialiaPub Date : 2025-02-04DOI: 10.1016/j.mtla.2025.102358
Daniel R. Sinclair, Nikhilesh Chawla
{"title":"Mechanisms for pore evolution and heterogeneity in laser powder bed fusion aluminum elucidated through x-ray microscopy","authors":"Daniel R. Sinclair, Nikhilesh Chawla","doi":"10.1016/j.mtla.2025.102358","DOIUrl":"10.1016/j.mtla.2025.102358","url":null,"abstract":"<div><div>Laser powder bed fusion (LPBF) of metallic components produces a unique combination of thermomechanical phenomena such as convection, vaporization, and keyholing. The resulting melt pool structure is not easily characterized in post-facto analysis of printed parts, making process-structure correlations very difficult. Here, structures produced by laser keyhole formation during LPBF of an aerospace aluminum alloy were studied through a simplified sample geometry and controlled remelting. The final distribution of pores within the solidified wall were imaged and quantified through high resolution x-ray microscopy and correlated to the remelted melt pool structure. Based on observations from this multimodal, quantitative analysis, a mechanism for the distribution of porosity is proposed. Novel effects of laser processing conditions on microstructures are thus described, highlighting a key source of heterogeneity across the scales of melt pools to thin 3D features.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102358"},"PeriodicalIF":3.0,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143313273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Phase transformation and austenite stability during thermomechanical processing of high (∼5%) Al added low-density medium Mn steel","authors":"Mukesh Kumar Yadav, Deepak Kumar, Navanit Kumar, Tapas Kumar Bandyopadhyay","doi":"10.1016/j.mtla.2025.102360","DOIUrl":"10.1016/j.mtla.2025.102360","url":null,"abstract":"<div><div>In this study, a high Al added low-density medium Mn steel has been developed by conventional melting casting route in an open-air induction furnace, followed by hot forging and hot rolling in the temperature range of 1050-800°C. Finally, it has been intercritically annealed at 750°C for 5, 30, 60, 120, and 180 minutes. The microstructural analysis shows the presence of dual-phase microstructure of delta ferrite and austenite in cast as well as hot forged specimens. While some of the austenite has been transformed to martensite (lenticular shape) in rolled specimen due to a higher cooling rate (water quenching) immediately after hot rolling. After 5 minutes of annealing, needle shape of reverted austenite and intercritical ferrite forms from martensite. As the annealing time increases to 30 minutes, the reverted austenite coalesces and undergoes further transformation into ferrite. This results in the formation of reverted austenite with needle and globular morphologies at 60 minutes of annealing. This annealing condition reveals the optimum mechanical stability due to its morphology and chemical composition, resulting in enhanced TRIP effect as compared to other annealing conditions. Further increase in annealing time to 120 and 180 minutes, volume fraction of reverted austenite decreases significantly due to more dissolution of reverted austenite to intercritical ferrite, leading to reduced TRIP effect. Specimen annealed for 60 minutes, possessing optimal mechanical stability of austenite, exhibits tensile properties with an ultimate tensile stress of 658.45±6 MPa and total elongation of 12±0.95 %, attributed to enhanced TRIP effect.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102360"},"PeriodicalIF":3.0,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MaterialiaPub Date : 2025-02-04DOI: 10.1016/j.mtla.2025.102359
Mariappan Parans Paranthaman , Harshida Parmar , Kaustubh Mungale , James W. Kemp , Haobo Wang , Ikenna C. Nlebedim , Uday Kumar Vaidya
{"title":"Extrusion compression molded critical rare earth free bonded permanent magnets","authors":"Mariappan Parans Paranthaman , Harshida Parmar , Kaustubh Mungale , James W. Kemp , Haobo Wang , Ikenna C. Nlebedim , Uday Kumar Vaidya","doi":"10.1016/j.mtla.2025.102359","DOIUrl":"10.1016/j.mtla.2025.102359","url":null,"abstract":"<div><div>Samarium iron nitride (Sm-Fe-N) bonded magnets have emerged as promising candidates for various industrial applications due to their exceptional magnetic properties. Compounds with magnetic material 95 wt fraction (wt.%) (∼74 vol%) and 97 wt.% (∼81 vol%) of SmFeN in a polyamide (PA12) polymer binder are manufactured using a batch mixer followed by compression molding. A maximum energy product <em>(BH)</em><sub>max</sub> of 186.21 kJ.m<sup>-3</sup> (23.4 MGOe) is achieved in the 95 wt.% bonded magnets; 97 wt.% magnets had a <em>(BH)</em><sub>max</sub> of 165.52 kJ.m<sup>-3</sup> (20.8 MGOe). It is found that the degree of alignment (DoA) of 99 % is achieved in the 95 wt.% magnets, whereas the 97 wt.% magnets are limited to a DoA of 90 % respectively. The high DoA can be attributed to low particle-particle interaction during the post-magnetic field alignment process. This research provides a useful insight of binder-particle interactions at very high magnet weight fractions and their effect on magnetic strength and performance.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102359"},"PeriodicalIF":3.0,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MaterialiaPub Date : 2025-02-04DOI: 10.1016/j.mtla.2025.102362
Xina Huang , Sirui Guo , Wenjing Chen
{"title":"Effect of initial grain size on dynamic recrystallization of ultra-large nuclear rotor steel 25Cr2Ni4MoV","authors":"Xina Huang , Sirui Guo , Wenjing Chen","doi":"10.1016/j.mtla.2025.102362","DOIUrl":"10.1016/j.mtla.2025.102362","url":null,"abstract":"<div><div>The effects of different initial grain sizes on dynamic recrystallization (DRX) of ultra-large nuclear rotor steel 25Cr2Ni4MoV based on the isothermal hot-compression tests under different deformation conditions were systematically investigated. The results show that the strain rate is faster, the smaller the initial grain size, the easier DRX occurs. The average grain size of DRX is positively correlated with deformation temperature, negatively correlated with strain rate, and positively correlated with initial grain size. At higher strain rates, the initial grain size has less effect on the average grain size of DRX. However, the degree of DRX is higher in the specimen with a smaller initial grain size. The DRX model was constructed of 25Cr2Ni4MoV with initial grain sizes of 33μm, 179μm, and 1577 μm based on the experimental data. The DRX average grain size models have good fitting accuracy, and the DRX percentage models are consistent with the DRX degree shown by the flow stress strain curves. when DRX occurs sufficiently and the strain rate is low, the larger the initial grain size is, the smaller the critical strain of DRX is, and the easier it is for DRX to occur.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102362"},"PeriodicalIF":3.0,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
MaterialiaPub Date : 2025-02-04DOI: 10.1016/j.mtla.2025.102361
A. Potenciano , A. Nicolay , A. Da Fonseca Alvarenga , O. Danylova , J. Dairon , M. Bernacki , B. Flipon , N. Bozzolo
{"title":"Statically recrystallized grain size as a function of prior stored energy level in the A-286 Fe-based superalloy","authors":"A. Potenciano , A. Nicolay , A. Da Fonseca Alvarenga , O. Danylova , J. Dairon , M. Bernacki , B. Flipon , N. Bozzolo","doi":"10.1016/j.mtla.2025.102361","DOIUrl":"10.1016/j.mtla.2025.102361","url":null,"abstract":"<div><div>A-286 alloy is a Fe-based superalloy used in various engines and gas turbine components. During manufacturing, this alloy is submitted to a solution heat treatment that provides good formability for the subsequent deformation steps. Hence, a good control of grain size evolution is required to avoid the formation of a broad grain size distribution or the growth of abnormally large grains. In this work, a well-controlled strain gradient has been generated by means of indentation tests at room temperature. A specific strain level, calculated by finite element simulations, and the associated dislocation density estimated by the EBSD technique, lead to the activation of selective grain growth during heat treatment after a given incubation time. This study on cold-deformed A-286 alloy allowed a quantitative assessment of recrystallized grain size dependence on stored energy and the identification of the critical stored energy value for grain nucleation, providing a better understanding of A-286 static recrystallization behavior.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102361"},"PeriodicalIF":3.0,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}