Search Results (75)

Limbal stem cell (LSC) transplantation is an important treatment for limbal stem cell deficiency (LSCD), but low efficacy in maintaining LSC stemness during in vitro expansion greatly affects its wider application. The primary contributing factors include a low proportion of stem cells and the lack of a stable, supportive microenvironment over prolonged culture. Rabbit corneal tissues preserved under deep cryogenic conditions for more than six months retain viable limbal stem cells (LSCs), and primary LSCs isolated from these tissues exhibit robust stem cell characteristics. It is noteworthy that the NLRP3/Caspase-1/IL-1β signaling axis was activated in corneal epithelial cells, and outer limbal layers preserved for one or two years. Based on these findings, a combined strategy integrating deep cryopreservation with IL-1β induction was established for the processing of limbal tissues. The combined cryogenic and IL-1β preconditioning yielded primary LSCs with maintained p63⁺ cell proportions, a reduction in K3⁺ differentiated cells from approximately 80% to 60%, and a 6.25-fold increase in colony-forming efficiency. In addition, an increased proportion of cells in the G2/M phase and enhanced proliferative capacity were observed. The enriched LSC population also exhibited improved stratified epithelial reconstruction potential. These findings identify an effective strategy for preserving and enriching LSCs from limbal tissue, providing a practical and efficient approach for LSC preparation prior to transplantation. Further in vivo studies will be important to validate the functional performance of these cells in ocular surface reconstruction. Full article

Due to excellent performance, polytetrafluoroethylene (PTFE), being sealing material, is widely used in chemical engineering, aerospace engineering, mechanical engineering, civil engineering, energy engineering and other sectors. However, due to obvious temperature drops in supplying or storing fluids, the mechanical behavior of PTFE under cryogenic conditions is still unclear. In this study, the creep mechanical performance of PTFE gaskets after cryogenic aging in liquid oxygen is experimentally investigated. The circular PTFE gasket samples are immersed into liquid oxygen for cryogenic aging treatment. The universal testing machine is utilized for material mechanic tests. Three different load levels, including 10 MPa, 15 MPa and 20 MPa, are designed and accounted for. It is found that the creep strain of PTFE exhibits three typical stages, namely the initial rapid increase phase, transition phase with a reducing growth rate, and stable linear growth phase. Moderate cryogenic immersion aging can effectively improve the creep resistance of PTFE, but excessive aging treatments will lead to mechanical property degradation of PTFE. The Burgers life prediction model is improved by introducing a nonlinear correction term, which can accurately predict the creep behavior of PTFE under different aging states. The present study can provide experimental evidence and a theoretical basis for a deep understanding of the mechanical response of PTFE materials under extreme cryogenic intermittent service conditions. Full article

A microalloyed high-carbon low-alloy steel was designed to clarify the combined effects of austenitizing temperature and deep cryogenic treatment (DCT) on microstructural evolution and mechanical performance. Specimens were austenitized at 770–900 °C, water-quenched, subjected to DCT at −196 °C, and subsequently tempered at 180 °C. Microstructural characterization by XRD, EBSD, and TEM indicates that the quenched microstructure is dominated by martensite and cementite, with retained austenite below 1% at moderate austenitizing temperatures. DCT does not fundamentally alter the martensitic morphology but promotes the transformation of retained austenite and induces substructure fragmentation, dislocation reorganization, and a more homogeneous lattice strain distribution. Concurrently, carbon redistribution during cryogenic exposure facilitates the formation of finely dispersed carbides. After tempering, partial recovery and stabilization of the martensitic substructure lead to reduced lattice distortion while maintaining a high density of effective strengthening features. Mechanical testing shows that DCT combined with appropriate austenitizing (770–790 °C) improves hardness and ultimate tensile strength with acceptable ductility, whereas excessive austenitizing at 900 °C results in severe grain coarsening and intergranular brittle fracture. The results demonstrate that optimized integration of microalloying and DCT enables a favorable strength–toughness balance in high-carbon tool steels. Full article

Aluminium is widely used in electrical and structural applications; however, its lower electrical conductivity compared to copper limits broader adoption in high-performance systems. Deep cryogenic treatment (DCT) and DCT followed by annealing (DCT+A) have recently appeared as promising techniques to refine microstructures and enhance functional properties in metallic materials. In this study, commercially pure aluminium was subjected to DCT and DCT+A with soaking hours of 6, 12, 18, and 24 at −196 °C. The results revealed that both DCT-12 and DCT+A-12 treatments produced significant grain refinement. XRD confirmed the smallest crystallite size (32.39 nm) and maximum dislocation density (9.53 × 10¹⁴ m⁻²) in DCT-12, while extended soaking of 18 h facilitated recovery, yielding larger crystallite sizes (52.82 nm), reduced density, and microstrain. EBSD analysis showed texture strengthening in the (100) and (111) planes and a notable transition from HAGB to LAGB fractions. TEM and Raman analysis further confirmed defect recovery and phonon coherence at longer soaking hours. Electrical conductivity and mobility were enhanced across all treated specimens, with peak values seen for DCT-18 (4.91 × 10⁷ S/m, 50.8 cm²/V·s) and DCT+A-18 (4.52 × 10⁷ S/m, 46.9 cm²/V·s). These findings confirm that 18 h of soaking is optimal, particularly when combined with annealing, and yields a stable microstructure, improved electron transport, and superior conductivity. Full article

T6 aging, involving solution treatment and artificial aging, is a widely adopted strengthening method for magnesium alloys due to its proven effectiveness. However, the integration of three or more sequential thermal treatments has been explored only sparingly, primarily due to the challenges associated with optimizing such multi-parameter processing systems. This study demonstrates that integrating a 12 h deep cryogenic treatment (DCT) before aging in a Mg–Al–Ca–Mn alloy optimizes mechanical performance, achieving a tensile strength of 343 MPa and 27.3% elongation. Microstructural analysis, based on electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM), reveals that the strength enhancement results from ~29 nm precipitate refinement, elevated dislocation density, and nanoscale sub-grain formation, while the ductility gains stem from the activation of non-basal slip systems and the suppression of microcrack propagation. These synergistic mechanisms enable superior strain accommodation, providing a clear framework for DCT-enabled sequential heat treatment design in high-performance magnesium alloys. Full article

Deep cryogenic treatment (DC) is widely applied to martensitic stainless steels to suppress the presence of metastable retained austenite (RA), which may otherwise transform into brittle martensite under deformation and degrade mechanical performance. In this study, a low-carbon 13Cr-2Ni-2Mo martensitic stainless steel was subjected to deep cryogenic treatment for 2 h, followed by tempering at 200–600 °C to investigate carbide evolution and its correlation with mechanical response. At 200 °C, undissolved M₂₃C₆ was observed, accompanied by an RA volume fraction of 8.43% which exhibited a hardness of 543.3 ± 5.1 Hv. When tempered at 400 °C, M₃C became predominant, corresponding to a hardness of 524.5 ± 5.1 Hv. At 500 °C, the simultaneous precipitation of M₃C, M₇C₃, and M₂₃C₆ carbides induced pronounced secondary hardening, which promoted the peak hardness of 559 ± 5.6 Hv. Further tempering at 600 °C resulted in carbide spheroidization M₂₃C₆, which resulted in a hardness reduction to 392.2 ± 3.9 Hv while enhancing ductility. These findings reveal that the tempering temperature plays a decisive role in controlling the carbide precipitation sequence and the stability of retained austenite, thereby enabling the design of an optimal strength–ductility balance in deep cryogenically treated martensitic stainless steels. Full article

The tension behaviors of Al-Mg alloys were tested, and the influences of deep cryogenic treatment (DCT) and grain size on their tensile properties were explored. Optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the evolution of the microstructure. It was concluded that the alloys with fine grain (FG) had a higher strain hardening capacity and strength, however, the alloys with coarse grain (CG) exhibited better plasticity. This can be explained by the alloy with fine grains having a higher density of grain boundary, which can hinder the motion of the dislocation; therefore, the deformation resistance was improved. For alloys with coarse grains, the dislocation has more freedom to move and is easier to rearrange, which is beneficial to the plasticity. Moreover, when given deep cryogenic treatment, the strength and plasticity of the alloys can be slightly improved, which can be attributed to the microplastic deformation that occurs during cryogenic treatment that can induce internal stress, as cold-induced internal stress is conductive in achieving a finer grain and higher density of dislocation. Full article

In this study, deep cryogenic treatment (DCT) was applied to cold work tool steels with different vanadium weights (Vanadis 4 and Vanadis 10) for 12, 24 and 36 h, and the changes in their mechanical properties and microstructures were examined. Compression, tensile, hardness, SEM–EDS, carbide size, XRD and Rietveld analyses were performed to examine the mechanical and microstructural properties of the cryogenically treated samples. In this study, increasing the cryogenic treatment time and vanadium weight ratio did not have a positive effect on the hardness, and it was determined that the most positive result in terms of tensile and compressive strength was obtained in the V4_DCT-24 sample. The results of this study showed that the cryogenic treatment formed secondary carbides, vanadium carbide (VC) and chromium carbide (Cr₇C₃), in vanadium cold work tool steels and reduced the amount of retained austenite (γ-Fe), transformed into martensite (α’-Fe) structures. Additionally, cryogenically treated Vanadis steels are thought to be usable in the metal processing industry, especially for cutting tools and molds. Full article

The extensive use of copper in thermal and electrical systems calls for constant performance enhancement by means of innovative material treatments. The effects on the microstructural, mechanical, and electrical characteristics of copper in deep cryogenic treatment (DCT) and deep cryogenic treatment followed by heat treatment (DCT + HT) are investigated in this work. Copper samples were treated for various soaking durations ranging from 6 to 24 h. Mechanical properties such as tensile strength, hardness, and wear rate were analyzed. In the DCT-treated samples, tensile strength increased, reaching a peak of 343 MPa at 18 h, alongside increased hardness (128 HV) and a refined grain size of 9.58 µm, primarily due to elevated dislocation density and microstrain. At 18 h of soaking, DCT + HT resulted in improved structural stability, high hardness (149 HV), a fine grain size (7.42 µm), and the lowest wear rate (7.73 × 10⁻¹⁰ mm³/Nm), consistent with Hall–Petch strengthening. Electrical measurements revealed improved electron mobility (52.08 cm²/V·s) for samples soaked for 24 h in DCT + HT, attributed to increased crystallite size (39.9 nm), reduced lattice strain, and higher (111) texture intensity. SEM–EBSD analysis showed a substantial increase in low-angle grain boundaries (LAGBs) in DCT + HT-treated samples, correlating with enhanced electrical conductivity. Overall, an 18 h soaking duration was found to be optimal for both treatments. However, the strengthening mechanism in DCT + HT is influenced by grain boundary stabilization and thermal recovery and is different to DCT, which is strain-induced enhancement. Full article

In this study, friction stir welding was first applied to the 1.4 mm thick TRIP590 steel sheets at a constant transverse speed of 100 mm/min and different rotation speeds from 200 to 500 rpm. Then, the obtained joints received deep cryogenic treatment in liquid nitrogen for 24 and 48 h, respectively. It was revealed that the content of retained austenite in the stir zone of the welded joints decreased from 3.3% to 0.2% when the rotation speed increased from 200 rpm to 500 rpm. The stability of retained austenite increased due to grain refinement and work hardening at low rotation speeds. After deep cryogenic treatment of the welded joints, the retained austenite in the stir zone partially transformed into martensite, which led to the precipitation of nano-sized carbide in the ferrite matrix and the release of local stress. As a result, both the strength and plasticity of the stir zone after 48 h of deep cryogenic treatment increased from 798 MPa, 15% to 927 MPa, 17% for the 200 rpm joint, and from 914 MPa, 14% to 1086 MPa, 16% for the 300 rpm joint during the tensile tests. Full article

To enhance the electrocatalytic performance of a flexible Pd@CFs catalyst for methanol oxidation, deep cryogenic treatment in liquid nitrogen was introduced. The effects of the frequency and time of the deep cryogenic treatment on the surface crystal orientation, microstructure morphology, mechanical performance, and electrocatalytic performance for methanol oxidation were studied. The results showed that when the frequency of the deep cryogenic treatment was 2 times and the deep cryogenic time was 24 h, the electrocatalytic performance of the catalyst was the best. Compared with the catalyst without deep cryogenic treatment, the activity and stability of the catalyst increased by about 33% and 41%, respectively. The activity and stability of the catalyst were about 43.4 times and 6.3 times that of the commercial Pd/C catalyst, respectively. After 500 cycles of CV testing, the performance of the catalyst decay rate was only 3.9%. Compared to the CFs, the tensile strength and the elongation rates of the catalyst increased by 24.6% and 57%, respectively. This is due to deep cryogenic treatment causing Pd grains to rotate from a disordered arrangement to an ordered arrangement, making the metal particles more dispersed and exposing more active sites, ultimately improving the electrocatalytic oxidation ability of methanol. The excellent electrocatalytic efficiency of Pd@CFs-24-2 coupled with its simple and easy preparation method has great potential for promoting the development of DMFCs. Full article

In this work, the microstructure, hardness, tensile and yield strength, and wear resistance of X210CrW12 steel are examined in relation to the impacts of deep cryogenic treatment. In order to achieve this, deep cryogenic treatment at −180 °C was applied to X210CrW12 steel samples for 12, 18, 24, and 36 h following quenching. Following the cryogenic treatments, a tempering heat treatment was applied to the samples at 300 °C for two hours. Experimental results showed that deep cryogenic treatment significantly improved the mechanical properties of X210CrW12 steel. The best mechanical properties were obtained after applying deep cryogenic treatment for 24 and 36 h. The cryogenic treatment showed the most dominant effect on wear resistance. As a result of the wear tests performed with the pin-on-disk method, it was determined that the wear rate of the sample subjected to cryogenic treatment for 36 h was 59.37% less than that of the conventionally hardened sample. The deep cryogenic treatment applied for 36 h provided the highest hardness increase of 12.06%. Compared to the conventionally hardened sample, the tensile and yield strength in the steel subjected to deep cryogenic treatment for 24 h is up to 11.02% and 11.35% higher. As a result of microstructural analysis, it was determined that it provides cryogenic new carbide precipitation, increases carbide density, and provides a more homogeneous carbide distribution. Full article

A novel coupled processing method (PDCT) that associated deep cryogenic treatment (DCT) with a high pulsed magnetic field (PMT) was investigated to improve the performance of an as-cast TC4 aero-titanium alloy. Through XRD, SEM, TEM, EBSD, and a properties test, its microstructure and tensile properties and their relationship were investigated. The results show that in comparison with the untreated samples, in the PDCT alloys, the amount of nano-sized precipitates and dislocation density are increased, and this phenomenon is characterized by their combed dislocation morphology. The grain sizes are refined and rounded, and the deformed grains are enhanced, together with the enhancement of low-angle grain boundaries in grains and the transformation from the β phase to the α phase. The (112) crystal orientation is apparently strengthened. The tensile strength, elongation, and fracture energy of the optimized PDCT sample are 921.4 MPa, 7.6% and 5.47 × 10⁷ J/m³, which increased by 4.9%, 28.8% and 80.5% compared with the untreated sample, respectively. The tensile fracture exhibits rheological deformation along the phase boundaries. The strength–toughness mechanisms are mainly attributed to the texture, precipitation, dislocation and fine grain strengthening, which stem from the cold contraction and lattice distortion of DCT and the main magneto-plasticity effect of PMT, together with their coupling effects. Full article

The objective of this research is to enhance the mechanical and corrosion resistance properties of a cast Ni-Al bronze (NAB). To achieve this, the effect of deep cryogenic treatment (DCT), a process that has shown promise in other alloys, is initially investigated. It is demonstrated that, in the case of NAB, DCT induces only minor microstructural changes, which do not lead to any significant improvement in its properties. Consequently, it is proposed that a combined treatment be employed, involving annealing either before or after DCT. The results indicate that annealing at 675 °C for 2 h following cryogenic treatment at −180 °C increases the yield strength by approximately 11%. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in simulated seawater further confirm that this combination results in the formation of oxide layers with enhanced protective capacity. These improvements are attributed to the significant refinement and homogenization of the microstructure, including the globularization of the kI, kII, and, particularly, kIII phases, and an increase in the precipitation of the kIV phase in a finer and more homogeneous form within the alpha phase. Full article

In recent years, consumers have become increasingly interested in natural, biodegradable and eco-friendly composites. Eco-friendly composites manufactured using natural reinforcing filling materials stand out with properties such as cost effectiveness and easy accessibility. For these reasons, in this research, a composite workpiece was specially manufactured using eco-friendly jute fibers. Two cost-effective cutting tools were specially produced to ensure high-quality machining of this composite workpiece. One of these specially manufactured cutting tools was subjected to DC&T (deep cryogenic treatment and tempering) processes to improve its performance. At the end of the research, when the lowest and highest Fd (delamination factor) values obtained with DC&T-T1 and T1 cutting tools were compared, it was observed that 5.49% and 6.23% better results were obtained with the DC&T-T1 cutting tool, respectively. From the analysis of the S/N (signal-to-noise) ratios obtained using Fd values, it was found that the most appropriate machining parameters for the composite workpiece used in this investigation were the DC&T-T1 cutting tool, a 2000 rev/min spindle speed and a 100 mm/min feed rate. Through ANOVAs (analyses of variance), it was discovered that the most significant parameter having an impact on the Fd values was the spindle speed, with a rate of 53.01%. Considering the lowest and highest Ra (average surface roughness) values obtained using DC&T-T1 and T1 cutting tools, it was seen that 19.42% and 16.91% better results were obtained using the DC&T-T1 cutting tool, respectively. In the S/N ratio analysis results obtained using Ra values, it was revealed that the most appropriate machining parameters for the composite workpiece used in this investigation were the DC&T-T1 cutting tool, a 2000 rev/min spindle speed and a 100 mm/min feed rate. In the ANOVAs, it was revealed that the most significant parameter having an effect on the Ra values was the feed rate at 37.86%. Full article