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Tailoring the collagen film structural properties via direct laser crosslinking of star-shaped polylactide for robust scaffold formation
摘要： Application of restructured collagen-based biomaterials is generally restricted by their poor mechanical properties, which ideally must be close to those of a tissue being repaired. Here, we present an approach to the formation of a robust biomaterial using laser-induced curing of a photosensitive star-shaped polylactide. The created collagen-based structures demonstrated an increase in the Young’s modulus by more than an order of magnitude with introduction of reinforcing patterns (from 0.15±0.02 MPa for the untreated collagen to 51.2±5.6 MPa for the reinforced collagen). It was shown that the geometrical configuration of the created reinforcing pattern affected the scaffold’s mechanical properties only in the case of a relatively high laser radiation power density, when the effect of accumulated thermomechanical stresses in the photocured regions was significant. Photo-crosslinking of polylactide did not compromise the scaffold’s cytotoxicity and provided fluorescent regions in the collagen matrix, that create a potential for noninvasive monitoring of such materials’ biodegradation kinetics in vivo.
关键词： mechanical properties,collagen,reinforcements,photopolymerization,biocompatible polymers,riboflavin
更新于2025-11-21 11:24:58
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Formation of ordered defect structures in lithium niobate crystals of different chemical composition at non-equilibrium processes of different nature
摘要： Ordered defective structures in lithium niobate crystals have been established. The phenomenon is a result of non-equilibrium processes of a different nature: photo-induced light scattering, laser ablation, and creation of cracks during relieving mechanical stresses. The shape of such structures depends on the nature and energy that affect a crystal. A number of concentric areas with a different density of laser-induced defects with a changed refractive index appear during photoinduced light scattering. Concentric clusters of microdomains appear in a macrodomain of another sign at laser ablation as a result of local switching under impulse laser radiation. A number of microcracks with a fractal structure appear near main macro-crack during cracking under mechanical stress. Thus, appearance of ordered defective structure occurs not only in the local spot of direct exposure to laser radiation, mechanical stress, etc., but also in some volume of a crystal around it.
关键词： Doping,Laser ablation,Lithium niobate,Mechanical stress,Defective structure,Photorefractive effect
更新于2025-11-21 11:24:58
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Laser additive manufacturing of Zn-2Al part for bone repair: Formability, microstructure and properties
摘要： Zinc (Zn) alloys are promising bone repair materials due to their inherent degradability, favorable mechanical property and biocompatibility. In this investigation, laser powder bed fusion (LPBF) known as a representative additive manufacturing technique was applied to fabricate Zn-2Al (wt.%) part for bone repair application. A low energy density (Ev) led to the formation of pores and resultant insufficient densification rate due to the high liquid viscosity within the molten pool. In contrast, a high Ev caused the evaporation of Zn powder and resultant failure of LPBF. With Ev increasing, the obtained grains and the precipitated lamellar eutectic structure contained η-Zn and α-Al phase became coarsened, which could be attributed to the enhanced heat accumulation and consequently decreased cooling rate. At optimized Ev of 114.28 J/mm3, fully dense Zn-2Al part with a densification rate of 98.3±1.4% was achieved, which exhibited an optimal hardness of 64.5±1.8 Hv, tensile strength of 192.2±5.4 MPa and a moderate corrosion rate of 0.14 mm/year. In addition, in vitro cell tests confirmed its good biocompability. This study indicated that LPBF processed Zn-2Al part was a potential material for bone repair.
关键词： Zn alloys,laser additive manufacturing,mechanical properties,degradation rate,biocompability
更新于2025-11-21 11:18:25
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Development of a high strength Al–Zn–Si–Mg–Cu alloy for selective laser melting
摘要： Despite additive manufacturing processes are already widely used in several industrial applications, there are few materials that are specifically designed and optimized for these technologies. Currently, only few Al alloys are available on the market and employed for 3D printing of structural parts. In particular, SieMg bearing alloys are the most common Al alloys for additive manufacturing, featuring high processability but moderate mechanical properties. By this work, we studied the effect of Si addition on the hot cracking susceptibility of a high strength AleZneMgeCu alloy. A preliminary activity has been carried out by blending AleZneMgeCu and AleSieMg powders and analysing their microstructure and properties achieved after selective laser melting. Eventually a new AleZneSieMgeCu alloy has been designed, produced as powder alloy by gas atomization and tested. The microstructure and phase transformations of the new alloy has been investigated by synchrotron X-ray diffraction, differential scanning calorimetry and microscope analysis. The AleZneSieMgeCu alloy processed by selective laser melting featured a relative density of 99.8%, no hot cracks were noticed within the investigated microstructures. The ability of the new alloy to respond to aging starting from both as built and solution annealed conditions has been also evaluated. A good response to direct aging (directly from as built condition) was demonstrated, featuring yield strength and ultimate tensile strength of 402 and 449 MPa, respectively, and hardness of 174 HV after optimized aging at 165 (cid:1)C for 2 h.
关键词： Differential scanning calorimetry,Metal additive manufacturing,Mechanical properties,Synchrotron X-ray diffraction,High strength Al alloy
更新于2025-11-21 11:18:25
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Extraction of rare earth oxides from discarded compact fluorescent lamps
摘要： Discarded CFL samples are evaluated as a potential source of REEs (Y, Eu, Ce, Tb). The phosphors powder obtained from mechanical separation contains 31% rare earth values. The quantitative XRD analysis of phosphor sample yielded 39.9% red (YOX: Y1.90Eu0.10O3), 14.6% green (CAT: Al11Ce0.67MgO19Tb0.33), and 21.4% blue (BAM: Al10.09Ba0.96Mg0.91O17: Eu2+) phosphor along with 14.1% silica. Planetary ball milling was found promising in the liberation of REEs from given phosphor sample. A short milling of 20–30 min and 3–4 M acid concentration was found adequate for optimal recovery (> 90%) of REEs. Calcination of the precipitates resulted in the formation of REO with Y-Eu purity of > 98% and > 90% recovery rate. Eu, Y phase dissolution behavior was found completely different than Ce, Tb phase due to inert nature of Al11Ce0.67MgO19Tb0.33 till 120 min milling and 6 M acid concentration in leaching. Excessive milling promotes overall dissolution along with impurities dissolution and which further restrict the precipitation process. Based on the complete material balance 13 g of a mixed oxide of Y and Eu can be obtained from 100 units of CFLs.
关键词： Discarded CFL,Phosphor,Rare earth elements,Leaching,Mechanical milling
更新于2025-11-21 11:18:25
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Ultra-flexible perovskite solar cells with crumpling durability: toward a wearable power source
摘要： Perovskite materials hold great potential as photovoltaic power sources for portable devices owing to their mechanical flexibility and high performance; however, the flexibility and e?ciency require further improvement to attain practical viability. We investigated the mechanical fracture behavior of polycrystalline perovskite films by varying the substrate thickness and applying the neutral plane concept. This enabled us to fabricate a crack-free perovskite film on an ultra-thin substrate (B2.5 mm) and to demonstrate ultra-flexible solar cells with high e?ciency (17.03%) with unprecedented flexibility sustained after 10 000 cycles of bending at a 0.5 mm radius. This represents a high e?ciency of 13.6% for large-area flexible perovskite solar cells (1.2 cm2), fabricated by using a hybrid transparent electrode composed of a metal mesh grid and conducting polymer. Using a protective layer to achieve the neutral plane concept, our ultra-flexible perovskite solar cells are demonstrated to be durable even after 100 crumpling cycles. Our approach paves the way to fabricate flexible perovskite solar cells for portable power sources.
关键词： wearable power source,Perovskite solar cells,mechanical durability,neutral plane concept,flexible
更新于2025-11-21 10:59:37
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A MEMS BPSK to ASK converter
摘要： Purpose – The purpose of this paper is to investigate the feasibility of using micro electromechanical systems (MEMS) to convert a binary phase shift keying (BPSK) signal to a simpler amplitude shift keying (ASK) scheme. Design/methodology/approach – The prototype is designed within the SOIMUMPs? fabrication process constraints. The fabrication constraints imposed geometric limitations on what could be tested. These constraints were used to build a mathematical model, which in turn was used to optimize the response using MATLAB?. The optimized design was tested using ?nite element analysis with CoventorWare?, and ?nally lab tests on the fabricated device were performed to con?rm theoretical predictions. Findings – Theoretical predictions compared well with lab measurements on a prototype device measuring 2.9 mm2. The prototype was tested with a carrier frequency of 174 kHz at a BPSK data rate of 3 kHz and carrier amplitude of 6 V. With these parameters, ASK modulation indices of 0.96 and 0.94 were measured at the two output sensors. Originality/value – This study provides a MEMS solution for BPSK to ASK conversion. The study also identi?es what limits betterment of the modulation index and data rate. Such a device has potential application in wireless sensor network (WSN) nodes that have energy harvesters and sensors that are also built in MEMS. Being a MEMS device, it can facilitate integration in such WSN nodes and, hence, potentially reduce size and costs.
关键词： Modulation index,Mixer,ASK detector,Micro electro mechanical systems (MEMS),BPSK converter
更新于2025-11-14 17:28:48
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Precipitation behavior of selective laser melted FeCoCrNiC0.05 high entropy alloy
摘要： Interstitial elements are e?ective to strengthen high entropy alloys (HEAs). In this work, FeCoCrNiC0.05 was prepared by selective laser melting (SLM) followed by annealing. The e?ects of annealing on the microstructures and mechanical properties of the SLMed FeCoCrNiC0.05 were investigated. Results show that, nano-scale Cr23C6-type carbides can precipitate under annealing conditions, leading to higher yielding strength. The SLMed FeCoCrNiC0.05 annealed at 1073 K for 0.5 h has a yielding strength of 787 MPa and an elongation of 10.3%. Precipitation kinetics in SLMed FeCoCrNiC0.05 has been established according to Avrami formula. The high strength can be attributed to solid solution hardening, precipitation hardening and cell-like structures.
关键词： Precipitation kinetics,Hardening mechanism,Selective laser melting,Mechanical properties,High entropy alloy
更新于2025-11-14 17:04:02
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Preparation of ellipsoidal rod-shaped silica nanocomposite abrasives by Chromium ion/PEG200 induced method for sapphire substrates chemical mechanical polishing
摘要： Abrasive is vital to sapphire substrates chemical mechanical polishing and provides the most critical support for ?attening of sapphire. This work proposed a method to prepare ellipsoidal rod-shaped silica nanocomposite abrasives in order to increase the material removal rate and improve the surface roughness, which were applied to chemical mechanical polishing on sapphire substrates. Ellipsoidal rod-shaped silica nanocomposite abrasives were prepared by Chromium ion/PEG200 induced method. In this work, the synthesis process of ellipsoidal rod-shaped silica nanocomposite abrasives was discussed. As an inducing agent, Chromium compounds were bonded with two SiO2 particles via chemical bonds. And ellipsoidal rod-shaped silica nanocomposite abrasives were coated by PEG200 via hydrogen bonds. Results from X-ray photoelectron spectroscopy and time-of-?ight secondary ion mass spectroscopy revealed the occurrence of solid-state chemical reactions. The contact angle tests indicated the polishing liquid containing ellipsoidal rod-shaped silica nanocomposite abrasives had a good wettability. Ellipsoidal rod-shaped silica nanocomposite abrasives showed an excellent chemical mechanical polishing performance with a higher material removal and a lower surface roughness due to an excellent combination of chemical effect and mechanical effect occurred between ellipsoidal rod-shaped silica nanocomposite abrasives and sapphire substrates. A material removal model was built to describe the polishing behavior of ellipsoidal rod-shaped silica nanocomposite abrasives.
关键词： Polishing mechanism,Sapphire substrates,Ellipsoidal rod-shaped silica nanocomposite abrasives,Chemical mechanical polishing
更新于2025-11-14 15:27:09
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Polycrystal Synthesis, Crystal Growth, Structure, and Optical Properties of AgGaGe <sub/><i> <i>n</i> </i> </sub> S <sub/> 2( <i> <i>n</i> </i> +1) </sub> ( <i>n</i> = 2, 3, 4, and 5) Single Crystals for Mid-IR Laser Applications
摘要： AgGaGenS2(n+1) crystal is a series of quaternary for mid-IR laser applications of nonlinear optical materials converting a 1.064 μm pump signal (Nd:YAG laser) to 4?11 μm laser output, but only AgGaGeS4 has attracted the most attention, remaining the other promising AgGaGenS2(n+1) crystal whose physicochemical properties can be modulated by n value. In this work, AgGaGenS2(n+1) (n = 2, 3, 4, and 5) polycrystals are synthesized by vapor transport and mechanical oscillation method with di?erent cooling processes. High-resolution X-ray di?raction analysis and re?nement have revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2, resulting in the excellent nonlinear optical property, and the distortion of tetrahedron with the variation of n value causes the discrepancy of physicochemical property. Besides, using the modi?ed Bridgman method, AgGaGenS2(n+1) single crystals with 15 mm diameter and 20?40 mm length have been grown. We have discussed the structure and composition of AgGaGenS2(n+1) by XPS spectra and analyzed the three kinds of vibration modes of tetrahedral clusters by the Raman spectra. The Hall measurement indicates that the AgGaGenS2(n+1) single crystals are p-type semiconductor, and the carrier concentration decreases with the increasing n value. All the transmittances of as-grown AgGaGenS2(n+1) samples exceeds 60% in the transparent range, especially the transmittance of AgGaGe2S6, is up to 70% at 1064 nm, and the band gap of as-grown crystal increases from 2.85 eV for AgGaGe2S6 to 2.92 eV for AgGaGe5S12. After a thermal annealing treatment, the absorptions at 2.9, 4, and 10 μm have been eliminated, and the band gap changed into the range of 2.89?2.96 eV.
关键词： Hall measurement,nonlinear optical materials,thermal annealing treatment,vapor transport,AgGaGenS2(n+1),Bridgman method,Raman spectra,mid-IR laser applications,XPS spectra,mechanical oscillation method
更新于2025-11-14 15:27:09