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Homogeneous Anodic TiO <sub/>2</sub> Nanotube Layers on Ti–6Al–4V Alloy with Improved Adhesion Strength and Corrosion Resistance
摘要： Hexagonal TiO2 nanotubes (TNTs) arrays are generally fabricated on Ti-based substrates for some biomedical purposes, but the TNT layers constructed on conventionally processed Ti alloys are usually inhomogeneous because the substrates typically contain both the α and β phases. In this work, high-pressure torsion (HPT) is applied to obtain a saturated single α-phase microstructure in Ti–6Al–4V alloys via strain-induced β phase dissolution. Homogeneous anodic TNT layers with three different morphologies, one-step nanoporous, one-step nanotubular, and two-step nanoporous structures, are electrochemically fabricated on the ultrafine-grained (UFG) Ti–6Al–4V alloy substrates after HPT processing, whereas the TNT layers prepared on coarse-grained substrates are normally inhomogeneous. More notably, the TNT layers show significantly improved adhesion strength to the UFG substrate as well as better corrosion resistance compared to those on the conventionally processed Ti–6Al–4V substrates. X-ray diffraction analysis, scanning electron microscopy in combination with electron backscatter diffraction, and transmission electron microscopy indicate that the improvement is due to a larger dislocation density in the UFG substrate as well as strain-induced β phase dissolution.
关键词： high-pressure torsion,homogeneity,TiO2 nanotubes,adhesion strength,strain-induced phase transformation
更新于2025-11-21 11:03:13
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<p>A multifunctional-targeted nanoagent for dual-mode image-guided therapeutic effects on ovarian cancer cells</p>
摘要： Nanomedicine has emerged as a novel therapeutic modality for cancer treatment and diagnosis. Lipid–polymer hybrid nanoparticles (LPHNPs) are core–shell nanoparticle (NP) structures comprising polymer cores and lipid shells, which exhibit complementary characteristics of both polymeric NPs and liposomes. However, it is difficult to wrap perfluoropentane (PFP) into core–shell NPs in the existing preparation process, which limits its application in the integration of diagnosis and treatment. Methods: The folate-targeted LPHNPs-loaded indocyanine green/PFP-carrying oxygen (TOI_HNPs) using a combination of two-step method and solution evaporation technique for the first time. The essential properties and dual-mode imaging characteristics of developed NPs were determined. The cellular uptake of TOI_HNPs was detected by confocal microscopy and flow cytometry. The SKOV3 cell viability and apoptosis rate were evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay and flow cytometry. The ROS was demonstrated by fluorescence microplate reader and the expression of hypoxia-inducible factor 1-alpha (HIF-1α) and IL-6 was detected by Western blot. Results: TOI_HNPs showed spherical morphology with particle size about (166.83±5.54) nm and zeta potential at -(30.57±1.36) mV. It exhibited better stability than lipid NPs and higher encapsulation efficiency as well as active targeting ability than poly (lactic-co-glycolic acid) (PLGA) NPs. In addition, the novel NPs could also act as the contrast agents for ultrasound and photoacoustic imaging, providing precision guidance and monitoring. Furthermore, TOI_HNPs-mediated photo–sonodynamic therapy (PSDT) caused more serious cell damage and more obvious cell apoptosis, compared with other groups. The PSDT mediated by TOI_HNPs induced generation of intracellular ROS and downregulated the expression of HIF-1α and IL-6 in SKOV3 cells. Conclusion: This kind of multifunctional-targeted nanoagent may provide an ideal strategy for combination of high therapeutic efficacy and dual-mode imaging guidance.
关键词： core-shell nanoparticle,ultrasound,photo-sonodynamic therapy,phase transformation,photoacoustic imaging,laser
更新于2025-11-14 17:03:37
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Changes of optical transition models caused by crystal structural changes in CaSe2O5
摘要： The present work concerns calcium pyroselenites CaSe2O5 with two independent crystal structures, their di?erence physical properties and phase transformations. α-CaSe2O5 in orthorhombic form shows 2D calcium oxide anionic layers whereas new compound β-CaSe2O5 crystallizes in monoclinic space group C2/c. It's a new structure type with 1D calcium oxide thick chains which are further connected by Se2O5 dimers. Rietveld re?nement indicates that the weight fraction for α/β-CaSe2O5 mixture phase was found to be 84.5% and 15.5% for α- and β-CaSe2O5, respectively. Optical di?use re?ectance spectrum coupled with Kubelka–Munk ?t gives a result that α-CaSe2O5 adopts direct optical transition model while β-CaSe2O5 is an indirect semiconductor. The experimental result matches well with the prediction of theory calculation. The optical bandgap values were ?tted to be 4.74 and 4.12 eV for α- and β-CaSe2O5, respectively. Thermal analysis coupled with variable temperature powder XRD indicates the phase transformation between these two phases.
关键词： Selenite,Optical bandgap,Rietveld re?nement,Phase transformation
更新于2025-09-23 15:23:52
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Effect of laser forming on mechanical properties of multiple-phase steels by using a thermal–microstructure–mechanical model
摘要： Based on a forming temperature-controlled mixed strain-hardening law, a temperature-controlled thermal–microstructure–mechanical model was developed to predict the deformation in ferrite–martensite dual-phase steel before and after complex laser forming. Phase transformation in dual phase steel was predicted by coupling a kinetic transformation model with the developed model during laser forming. The corresponding algorithm of the constitutive model was used in three-dimensional finite element method to simulate the material deformation and mechanical properties during the laser forming. The simulated results agree well with the experimental results. Laser forming influences the mechanical properties of the material significantly, leads to bending deformation of the scanned sample and induces a ferrite-to-martensite transformation. The influence of scanning line number on the tensile strength and bending deformation of the scanned specimen was investigated. The tensile strength and bending angle are related positively to the number of scanning lines on the sample.
关键词： Stress-strain curve,Phase transformation,Thermal–microstructure–mechanical model,Sheet metal,Laser forming
更新于2025-09-23 15:23:52
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Millimeter-scale single-crystalline semiconducting MoTe <sub/>2</sub> via solid-to-solid phase transformation
摘要： Among the Mo- and W-based two-dimensional (2D) transition metal dichalcogenides (TMDCs), MoTe2 is particularly interesting for phase-engineering applications, because it has the smallest free energy difference between the semiconducting 2H phase and metallic 1T’ phase. In this work, we reveal that, under the proper circumstance, Mo and Te atoms can rearrange themselves to transform from a polycrystalline 1T’ phase into a single-crystalline 2H phase in a large scale. We manifest the mechanisms of the solid-to-solid transformation by conducting the density functional theory calculations, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The phase transformation is well described by the time-temperature-transformation diagram. By optimizing the kinetic rates of nucleation and crystal growth, we have synthesized single-crystalline 2H-MoTe2 domain with a diameter of 2.34 mm, centimeter-scale 2H-MoTe2 thin film with a domain size up to several hundred micrometers, and the seamless 1T’-2H MoTe2 coplanar homojunction. The 1T’-2H MoTe2 homojunction provides an elegant solution for ohmic contact of 2D semiconductors. The controlled solid-to-solid phase transformation in 2D limit provides a new route to realize wafer-scale single-crystalline 2D semiconductor and coplanar heterostructure for 2D circuitry.
关键词： 1T’-2H interface,phase transformation,single crystal,MoTe2 film
更新于2025-09-23 15:23:52
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Generation and distribution of residual stress during nano-grinding of monocrystalline silicon
摘要： Residual stress generated in grinding process of monocrystalline silicon can cause the wafer warpage, and di?culties in subsequent processes such as holding and scribing. It can also lead to the formation of cracks and the occurrence of corrosion, which is harmful for electrical performance of silicon component. In this study, with the method of step-wire wet etching, the phase transformation and distribution of residual stress in ground silicon wafer were examined by confocal laser micro-Raman spectroscopy. As the etching depth going down, the residual stress exhibits in the trends of decreasing of compressive stress and following a scatter distribution of tensile stress. During the nano-grinding processes of monocrystalline silicon, the generation mechanism of residual stress is computed by a series of the molecular dynamic (MD) simulation. Subsurface damage (SSD) in the form of phase-transformed silicon is observed, and the depth of SSD varies by the depth of cut. The volume shrinkage of phase-transformed silicon is also studied to explain the grinding mechanism and the reason for inducing residual stress of ground silicon. By adopted the Stony theory and volume shrinkage rate of amorphous phase from MD results, a theoretical model is established to determine the trend of compressive stress in subsurface of ground silicon.
关键词： monocrystalline silicon,residual stress,nano-grinding,phase transformation,molecular dynamics
更新于2025-09-23 15:21:21
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Influence of diamond tool chamfer angle on surface integrity in ultra-precision turning of singe crystal silicon
摘要： Ultra precision diamond machining enables the economical production of freeform optics on infrared materials such as silicon. To produce optics with acceptable surface integrity, it is important to have a good understanding of process-work material interaction between diamond tool and brittle and hard single crystal IR materials. Chamfered cutting edges are known to have high strength, which makes them suitable for machining difficult-to-cut materials. This study investigates the influence of chamfer angle on the surface integrity of silicon. Diamond tool chamfer angles of ? 20°, ? 30°, and ? 45° are considered under practical diamond turning conditions of single crystal silicon. State-of-the-art techniques were used to investigate the surface integrity of the machined silicon surfaces. The results show that chamfer angle of 30° yields more favorable results compared to 20° and 45° under the conditions tested. The results indicate the complex interplay between tool geometry and process parameters in reaching an acceptable level of surface integrity. A machinability map indicating ductile and brittle machining conditions for 30° chamfered diamond tool has been presented which includes directly transferable knowledge to the precision machining industry.
关键词： Silicon,Surface integrity,Phase transformation,Diamond machining
更新于2025-09-23 15:21:21
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A study of deformation behavior and phase transformation in 4H-SiC during nanoindentation process via molecular dynamics simulation
摘要： The deformation behavior and phase transformation of 4H silicon carbide (4H-SiC) during nanoindentation process is investigated with a cube corner diamond indenter through molecular dynamics simulation. It is found through the research that the basal dislocations are most likely to be generated in (0001) face and the indentation process contributes to the distortion of 4H-SiC lattice. In addition, phase transformation from 4H-SiC to 3C-SiC is firstly observed via MD simulations during indentation process. Cross-sectional observation in (12 10) plain shows that 3C-SiC layers appear firstly during nanoindentation process, and the layers are observed at small indentation depth. 3C-SiC grain is generated based on 3C-SiC layers, and the transformation is more likely to appear at larger indentation depth. The phase transformation from 4H-SiC to 3C-SiC results from the shear stress induced by indenter during loading process. 3C-SiC grain and layers are both generated from the slip of 3C seeds under the influence of shear stress, and the condition of 3C-SiC grain formation is stricter. Moreover, the P-h curve is studied and the vertical deformation mode during indentation process on 4H-SiC can be reflected on P-h curve as small pop-in events. The findings are meaningful for the study of deformation mechanism of SiC and the application of SiC in precision machining.
关键词： molecular dynamics simulation,cube corner diamond indenter,3C-SiC grain,4H-SiC,phase transformation,3C-SiC layer
更新于2025-09-23 15:21:01
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Microstructure of a Tia??50??wt% Ta alloy produced via laser powder bed fusion
摘要： Ti–Ta alloys have been widely studied for biomedical applications due to their high biocompatibility and corrosion resistance. In this work, nearly fully dense and in situ alloyed Ti–50 wt% Ta samples were fabricated by the laser powder bed fusion (LPBF) of mechanically mixed powders. With increased exposure time, and thereby increased laser energy density, insoluble Ta particles were almost dissolved, and a Ti–50 wt% Ta alloy was formed. Cellular and dendritic structures were formed due to constitutional undercooling, which was caused by the high cooling rate of LPBF process. Both retained β phases and α″ phases were observed in the LPBFed Ti–50 wt% Ta alloy. The α″ phase was found at the boundary of the cellular structures, where the tantalum content was not high enough to suppress the bcc lattice transition completely but could suppress the β phase → α′ phase transition.
关键词： Cellular and dendritic structures,Phase transformation,Ti–Ta alloys,Laser powder bed fusion,Microsegregation
更新于2025-09-23 15:21:01
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Effective Separation and Recovery of Valuable Components from CIGS Chamber Waste via Controlled Phase Transformation and Selective Leaching
摘要： Copper indium gallium diselenide (CIGS) chamber waste formed during CIGS solar-cell production was subjected to two-stage sulfation roasting for controlled phase transformation and selective leaching to separate valuable components. Selenium was initially separated in the first stage of sulfation roasting. Under the optimal conditions, 99.96% of selenium was volatilized into gas in the form of selenium dioxide, and the remaining components were converted to sulfates. The second stage of roasting followed by water leaching was investigated for the separation and recovery of the remaining components in slag. Controlled phase transformation of sulfates was completed in the second stage roasting. Indium and gallium sulfates are converted to oxides, whereas CuSO4 remained nearly unchanged. Afterward, 95.90% of copper was selectively leached into liquor, and the leaching rates of indium and gallium were only 5.67% and 2.89%, respectively. Consequently, the content of mixed indium and gallium oxides in the leach residue was 91.09%. Exploratory experiments show that indium and gallium can be effectively separated via alkali leaching and precipitation. Therefore, effective separation of valuable metals from CIGS chamber waste was achieved based on the different physical and chemical properties of the components.
关键词： Phase transformation,Valuable components,Separation,Leaching,CIGS chamber waste
更新于2025-09-23 15:19:57