Materialwissenschaft und Werkstofftechnik最新文献

The controlled synthesis of two-dimensional nanocrystals of graphene particles instead of amorphous carbon quantum dots is highly challenging and requires tremendous efforts to optimize the reaction conditions. It has been observed that as a significant bio-compatible zero-dimensional material, graphene quantum dots are considered as a novel material for opto-electronics, energy, biological and environmental applications. However, very few are known about their utilization in photocatalytic degradation of pesticides, especially organochlorine pesticides which are resistant to removal by conventional wastewater treatment methods. In this work, graphene quantum dots were produced from rice husk at relatively low temperatures, resulting in an average particle size of 3.3 nm. The high resolution transmission electron microscopy clearly showed the formation of spherical quantum dots having lattice fringes and the selected area electron diffraction pattern showed the crystallinity of the graphene quantum dots. A study of photodegradation of three highly toxic organochlorine pesticides namely, dichlorodiphenyl trichloro ethane, cypermethrin and fenvalerate were carried out using as-synthesized graphene quantum dots from rice husk. Interestingly, all these pesticides were found to be degraded around 60 % to 70 % under visible light conditions. It confirmed that synthesized graphene quantum dots from rice husk can act as prominent photocatalyst for the degradation of pesticides and other pollutants.

The field of 4D printing has emerged as a promising technology in the realm of implantable medical devices. Unlike traditional 3D printing, 4D printing allows for the fabrication of materials that can change shape or function over time in response to external stimuli. This review paper provides an overview of the application of 4D printing in implantable medical devices, highlighting its potential benefits, challenges, and future directions. This paper provide an overview of 4D printing, exploring the application of 4D printing in implantable medical devices and discuss the advantages and challenges of 4D-printed implants. These advantages may include patient-specific customization, enhanced functionality and performance, and minimally invasive procedures. Additionally, the paper addresses the challenges and future prospective associated with material selection, fabrication techniques, scalability, and regulatory and ethical considerations in the context of 4D printing. By addressing these topics, this review paper aims to provide a comprehensive understanding of the application of 4D printing in implantable medical devices. It seeks to contribute to the existing body of knowledge in the field and inspire further research and innovation in this promising area of healthcare technology.

This study investigates the properties of tin oxide coatings employed in biomedical applications. The films were deposited on a clean glass substrate, preheated at 450 °C, applying the spray pyrolysis technique as the latter produces crystallized thin films without the need for further heat treatment. X-ray diffraction analysis showed that tin oxide films had a tetragonal structure characterized by a preferential orientation (111). The measurements of reflectance and transmittance revealed a wide optical band gap of 4.0 eV. Nanoindentation tests showed that the tin oxide coating, with a hardness of 5.9 GPa and a Young's modulus of 78 GPa, exhibited elastic-plastic behavior. In addition, tribological tests indicated that tin oxide coating had a very low coefficient of friction (μ=0.06), high wear resistance (wear rate 2.10⁻⁵ mm³ N⁻¹ m⁻¹) and good adhesion to the substrate (critical adhesion load of 5.55 N). It was also noticed that tin oxide thin films had antibacterial activity due to their nanocrystalline impurities. These properties make tin oxide perfectly acceptable for biomedical applications.

In order to meet the increasing demand for high-speed joining processes, laser beam micro welding is used to reproducibly weld metallic joining partners such as steel. Long weld seams or high cycle speeds, however, remain a challenge to achieve a constant welding depth throughout the entire welding process without major fluctuations. This paper shows the development and evaluation of a weld penetration depth control system based on interferometric measurement of the depth of the vapor capillary. High path speeds and small weld depths are challenging for real-time depth control. Therefore, the offline data of the interferometric measurements are used to implement an iterative learning control of the weld penetration depth. The quality of the control is verified by welding with and without spatial power modulation on 1.4301 steel while following a linear and sinusoidal trajectory.

The work reported here deals with fabricating iron oxide nanoparticles incorporated polyvinyl alcohol nanocomposite films via the solution-casting green route, characterized using various characterization techniques. X-ray diffraction analysis shows interaction of nanoparticles with the polyvinyl alcohol matrix, scanning electron microscopy shows surface morphology of crack-free films, energy dispersive spectroscopy indicates elemental purity, tensiometer analysis shows changing behavior of hydrophilic to hydrophobic, thermogravimetric analysis shows improved thermal stability, ultraviolet-visible spectroscopy shows tunable optical properties, and frequency response analysis shows improved electrical properties. A small incorporation (1 wt. %) of iron oxide nanoparticles has induced significant alternations in structural, wetting, thermal, optical, and electrical properties of the polyvinyl alcohol-based nanocomposite films. Results showed notable changes in the structural phases, water contact angle (39.5° to 97.7°), optical absorption edge (5.12 eV to 4.84 eV), indirect band gap (4.99 eV to 4.68 eV), direct bandgap (5.41 eV to 5.21 eV), and band tail (0.57 eV to 0.89 eV) from native polyvinyl alcohol to polyvinyl alcohol/iron oxide nanocomposite films. Enhancements were observed in refractive indices, optical conductivity, optical dielectric loss, thermal stability, dielectric constant, and dielectric loss on incorporating iron oxide nanoparticles into the polyvinyl alcohol matrix. The fabricated nanocomposite films might be a potential material for optoelectronic and microelectronics applications.

This study aimed to pioneer a transformative approach in orthopedic implant design by developing and analyzing a groundbreaking carbon-flax reinforced bioepoxy hybrid composite bone plate. The primary objectives of the present research were to enhance the bio-mechanical performance of orthopedic implants and explore the potential applications of the novel material for orthopedic implants. Hybrid composite plate was fabricated mimicking the human bone with the soft inner core and a rigid outer coating. Mechanical properties for the hybrid composite were obtained through material characterization studies as per ASTM standards. The hybrid composite bone plates were tested as per bio-mechanical test standard and the results were correlated with the finite element simulations. The maximum stress value in the experiments for the biomechanical four-point bending tests was 331.74 MPa, and the corresponding strain value was 0.0337. The maximum equivalent stress and strain values obtained from simulation were in line with the findings of the experiments. The current research signifies a paradigm shift in orthopedic implant technology. The carbon-flax bioepoxy hybrid composite offers remarkable potential for orthopedic applications, promising safer and more durable solutions for patients in need of bone repair or replacement.

Nickel-titanium alloys are produced via laser metal deposition using titanium carbide and titanium diboride as nucleating agents to refine the grain structure. The optimal process parameters are determined by analyzing the quality of the alloy formation. X-ray diffraction confirms the simultaneous presence of the B19′ martensitic phase and B2 austenitic phase in the nickel-titanium alloy fabricated by laser metal deposition. Tensile testing is performed on the samples at room temperature. The results show that adding mass fractions 0.9 % titanium carbide and titanium diboride effectively refines the grain size of the nickel-titanium alloy fabricated by laser metal deposition, leading to improved tensile properties. Specifically, the addition increases the tensile strength by 40 % and 70 %, and the elongation by 50 % and 60 %.

The thermal balance of injection molds is defined by the cooling channel layout. However, the fluid tempering of injection molds underlies certain restrictions concerning the thermal dynamic and the local limitation of the zone of influence. The optimal heat balance within the mold to minimize warpage cannot be solely achieved with conformal cooling channels. Ceramic heating coating systems applied by Thermal Spraying on the cavity wall are a novel tempering method for high heating rates and offer the possibility of a more local heat input. In terms of the thermal mold design, the position and size of local heating coating systems need to be determined. A methodology is proposed, which connects the optimization of part warpage by defining the necessary local heat flux within the mold with the determination of the heating coating placement. Due to the dependence of the coating placement on the heating time and the power, different decision criteria of these parameters are discussed with regard to the process efficiency. The developed methodology can calculate the necessary heating power distribution to homogenize the surface temperature and freeze time. A second step discretizes the heating power distribution to certain manufacturable heating zones.

Brazing of hot work steel with nickel-based filler metals is a widely used process for manufacturing casting tools. However, the formation of brittle phases in the joint impairs its mechanical properties. Reducing these intermetallic phases is an important aspect. Thermodynamic equilibrium calculations are used to estimate the change in melting range and apearance of intermetallic phases by adding different amounts of molybdenum to Ni 620. The filler metals are then produced and their solidus and liquidus temperatures are investigated using differential scanning calorimetry. Specimens of X37CrMoV5-1 are then brazed in a vacuum furnace and their microstructure is analysed by scanning electron microscopy/electron dispersive spectroscopy and their hardness properties by nanoindentation. The addition of molybdenum to the Ni 620 filler metal leads to the formation of chromium molybdenum boride rich phases and reduced hardness values in brazed joints. Manipulation of Ni 620 by molybdenum helps to improve relevant properties in brazing hot work steel.