Practical Approach to Eliminate Solidification Cracks by Supplementing AlMg4.5Mn0.7 with AlSi10Mg Powder in Laser Powder Bed Fusion

The range of available aluminum alloy powders for laser powder bed fusion (LPBF) is restricted to mainly Al–Si based alloys. Currently aluminum alloy powders, designed for lightweight application, based on Al–Mg (5000 series), Al–Si–Mg (6000 series), or Al–Zn–Mg (7000 series), cannot be processed by LPBF without solidification cracks. This has an impact on the potential of LPBF for lightweight applications. In fusion welding, solidification cracks are eliminated by using filler materials. This study aims to transfer the known procedure to LPBF, by supplementing EN AW-5083 (AlMg4.5Mn0.7) with AlSi10Mg. EN AW-5083 and two modifications (+7 wt.% and +15 wt.% AlSi10Mg) were produced by LPBF and analyzed. It was found that, in EN AW-5083, the solidification cracks have a length ≥200 µm parallel to the building direction. Furthermore, the solidification cracks can already be eliminated by supplementing 7 wt.% AlSi10Mg. The microstructure analysis revealed that, by supplementing AlSi10Mg, the melt pool boundaries become visible, and the grain refines by 40% relative to the base alloy. Therefore, adding a low melting point phase and grain refinement are the mechanisms that eliminate solidification cracking. This study illustrates a practical approach to eliminate solidification cracks in LPBF.

Carbon Black Replacement in Natural Rubber Composites Using Dry-Milled Calcium Carbonate, Soy Protein, and Biochar

Recent discoveries have shown that calcium carbonate and soy protein interactions can be used to reinforce rubber composites with improvements on the effective crosslink density and moduli. However, the method to incorporate the soy protein into the rubber matrix may be costly to scale up, since it involves microfluidization and drying steps prior to rubber compounding. In this work, a simpler process involving dry-milled calcium carbonate and soy protein was used to explore filler blends of calcium carbonate, soy protein, biochar, and carbon black. By blending these filler materials in various ratios, rubber composite samples with 40–50% of the carbon black replaced by sustainable alternatives were made. These composites had essentially the same tensile strength, with better toughness and elongation properties relative to the carbon black control. These composites would reduce dependence on petroleum and be more amenable to the rubber composite compounding infrastructure.

Assessment of the Influence of the Type of Filler Materials on the Properties of Cement Grouts

Cement grouts have many purposes in various civil engineering applications such as precast construction, soil stabilization and structural rehabilitation. Using filler materials as a component in cement grouts has been increasingly implemented. The incorporation of such fillers not only does improve the fresh and hardened properties of grouts but also contributes to the decarbonization of grouts by reducing the amount of Portland cement, thereby lowering the carbon footprint of grouting materials. This study aims at assessing the influence of various filler materials on the properties of cement grouts. Three different fillers were used in this study: commercial limestone, commercial pure dolomite, dolomitic quarry dust. These fillers were assessed in terms of their effect on the spread, flowability, cohesion and compressive strength at 3, 7 and 28 days. The results show that fresh properties of the grout were dependent on the type of fillers. Dolomitic quarry dust improved the workability and flowability more than the commercial limestone and dolomite did. The compressive strengths of cement grouts did not change significantly with the incorporation of the fillers. However, cement grout samples including quarry dust exhibited slightly higher 28-d compressive strength than other samples although the same mix had lower 1-d compressive strength than other mixes. This study highlights the benefits of utilizing quarry dust in cement-based binders without compromising the performance.

Investigation of wear mechanics and behaviour of NiCr metallic foam abradables

Current aero-engine sealing materials are reaching their operating limit, as manufacturers seek more efficient engines with longer service lives. Even when utilised in optimum conditions, current materials have inconsistencies in performance due to variabilities in their microstructure, which lead to undesirable responses and events. As such, a new generation of sealing materials is required. Metallic foams are one such material, given the opportunities that exist to both engineer material properties, and achieve relatively consistent microstructures when compared to the current class of thermally sprayed abradable materials. In this study, the abradability of a nickel (70%)–chromium (30%) (NiCr) alloy foam is investigated, with the role of cell size and filler material considered. Tests are performed on a representative high-speed test rig, where a flat blade is used to simulate an aero-engine incursion event. A series of in situ measurement techniques, such as force, temperature and stroboscopic wear measurements are used to characterise the incursion, with DIC (Digital Image Correlation) techniques also employed to investigate breakdown of the foam. Unfilled foams were shown to lead to high blade wear, with the inclusion of filler materials leading to load transfer and collapse of the foam away from the incursion site, along with improved fracture. Both load transfer and ligament collapse mechanisms were found to promote more favourable rub mechanics at all incursion rates tested.

Complications and Disasters After Minimally Invasive Tissue Augmentation with Different Types of Fillers: A Retrospective Analysis

Background The interest in youthful appearance and rejuvenating procedures is unbroken in our society. Besides surgical procedures, permanent fillers are utilized. The incorrect and unprofessional use of these substances, auto-injections in particular, have devastating results for patients and are challenging for the plastic surgeon. The aim of this retrospective study was to delineate the differences between permanent and non-permanent filler complications and appropriate treatment options. Methods We conducted a retrospective study and researched the hospital information system in the time period from 2001 to 2020. Patients with unprofessional use of permanent fillers, auto-injections and injections of unformulated substances were determined. Age, gender, localization, complications, length of hospital stay, comorbidities, histopathological workups and surgical salvage procedures were noted. Descriptive statistics were calculated. Results Seventeen patients were identified from 2001 till 2020. In four cases, auto-injections by the patients were the cause, whereas in the other patients the injections were performed by medical staff. Ages range from 18 to 57 years. Fourteen patients were female and three were male. The injected substances could be recognized as synthol, silicone, vaseline, fat tissue, hyaluronic acid as well as non-medical substances. Surgical procedures were necessary in eleven cases. One patient died because of the underlying diseases. Conclusion Our results indicate different sequels of filler materials injected in an unprofessional way, possible complications, conservative and surgical techniques to resolve these rare complications. We suggest a staged therapy adjusted to the clinical symptoms. Milder symptoms can be handled conservatively, whereas severe infections, skin breakdowns or persistent granuloma are justifying indications for surgical treatment. Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

A Review of the Recent Progress in the Development of Nanocomposites Based on Poly(ether-block-amide) Copolymers as Membranes for CO2 Separation

An inspiring challenge for membrane scientists is to exceed the current materials’ performance while keeping the intrinsic processability of the polymers. Nanocomposites, as mixed-matrix membranes, represent a practicable response to this strongly felt need, since they combine the superior properties of inorganic fillers with the easy handling of the polymers. In the global strategy of containing the greenhouse effect by pursuing a model of sustainable growth, separations involving CO2 are some of the most pressing topics due to their implications in flue gas emission and natural gas upgrading. For this purpose, Pebax copolymers are being actively studied by virtue of a macromolecular structure that comprises specific groups that are capable of interacting with CO2, facilitating its transport with respect to other gas species. Interestingly, these copolymers show a high versatility in the incorporation of nanofillers, as proved by the large number of papers describing nanocomposite membranes based on Pebax for the separation of CO2. Since the field is advancing fast, this review will focus on the most recent progress (from the last 5 years), in order to provide the most up-to-date overview in this area. The most recent approaches for developing Pebax-based mixed-matrix membranes will be discussed, evidencing the most promising filler materials and analyzing the key-factors and the main aspects that are relevant in terms of achieving the best effectiveness of these multifaceted membranes for the development of innovative devices.

Investigation of Hybrid Composite Properties Fabricated from Bagasse Fibers Reinforced with Al2O3 and SiC for Light Weight Applications

The primary purpose of this study was to investigate mechanical properties of hybrid composite fabricated from bagasse fibers reinforced with Al2O3 and SiC for automotive purposes. The technique applied was referred to as the hand layup technique for the fabrication of composite. The experiment was conducted based on Taguchi L9 orthogonal array design. Data shows that the maximum tensile and flexural strength were 39.9 and 56.1 MPa respectively. Hardness and impact strength were 75.05 HV and 14 J respectively. The results indicated that the increasing Al2O3 and SiC wt.% increase the tensile strength and after bagasse fiber wt.% reaches optimum values the tensile strength decreased. Increasing Al2O3 wt.%, increases flexural strength and after bagasse fiber and SiC wt.% reaches optimum values, flexural strength was decreased. Increasing bagasse fiber wt.% increases the hardness of composite, and increasing Al2O3 and SiC wt.% increases the hardness, then after reaching optimum values the hardness was decreased. Increasing Al2O3 wt.% after the optimum values decrease the impact strength, and increasing bagasse fiber and SiC wt.% increase impact strength. The developed hybrid composite material was found to be improved the properties of composites after addition of Al2O3 and SiC powder as filler materials. This thesis recommends higher institutes, automotive companies, manufacturing companies, the construction sector and the government to conduct on how to utilize this abundant waste of bagasse fiber resource.

Durability Investigation of Sulfur and Traditional Concrete within Aggressive Environments

An experimental study was conducted to evaluate durability (compressive strength and mass loss%) in the modified sulfur concrete within aggressive environments. The modified sulfur concrete was prepared by adding recycled polymeric and filler materials that showed a noticeable enhancement for modified sulfur concrete characteristics. A durability comparison between modified sulfur concrete and traditional concrete was investigated at normal and aggressive environments (10% HCl and 3% NaCl). A cuboid shape with size (50 × 50 × 50mm) was used in this research to investigate the durability of both modified sulfur and traditional concrete. The modified sulfur concrete characteristics revealed high stable structure than traditional due to preventing a process of crystallization of sulfur that modified with polymer and fillers. The compressive strength was 10.87 – 22.5% increased for modified sulfur concrete compared to the traditional concrete at the normal environment. In the aggressive environments, the modified sulfur concrete illustrated high resistance strength compared to the traditional concrete. The comparison revealed a significant impact for 10% HCl and 3% NaCl on the traditional concrete. The compressive strength decreased between (88.78 – 96.17) % for traditional concrete compared to modified sulfur concrete in 10% HCl solution and (84.25 – 95.06) % in 3% NaCl solution. Furthermore, mass loss % of the modified sulfur concrete indicated high resistance compared to the traditional concrete in both 10% HCl and 3% NaCl solutions.

Comparative Study on Performance of Regenerator for Miniature Pulse Tube Cryocooler with Metal Matrix Materials at Ultra High Frequencies

A Miniature Pulse Tube Cryocooler (MPTC) is the first selection for the cooling of IR sensors, infrared detectors, etc. in space technology. The regenerator is one of the key components to operate an MPTC at high efficiency. The objective of this study is to explore the possibilities of the different matrices as regenerator filler materials for MPTC operating at ultra-high frequencies. REGEN 3.3 is one of the best software available for the design and optimization of cryocooler regenerators. We have used REGEN 3.3 for numerical simulations of the three different regenerator matrix materials viz. stainless steel wire mesh screen (SS 635#), brass wire mesh screen (500#) and copper wire mesh screen (500#) at the hot end and cold end temperatures of 300[Formula: see text]K and 80[Formula: see text]K for COP, cooling power, total power losses and pressure losses, at an ultra-high frequency of 100[Formula: see text]Hz and 200[Formula: see text]Hz. The simulation results depict that the regenerator using stainless steel mesh screen shows better results than that of the brass mesh screen and copper mesh screen at 100[Formula: see text]Hz. However, the performance of brass mesh screen and copper mesh screen performs better than the stainless steel at 200[Formula: see text]Hz. Therefore, the proposed matrix materials can be used as regenerator materials for the MPTC at ultra-high frequencies with better performances.

Technology of welding and repair works of hydropower plants units

In the course of long-term operation of hydroelectric units, they are subject to wear and tear, which negatively affects the power generating capacity of the hydroelectric power station. The existing repair technology provides the restoration of the geometric dimensions of the impeller chamber of the hydraulic unit using an austenitic cladding layer. However, this technology is characterized by the occurrence of cracks and delamination of the deposited layer during post-repair operation, which is negatively reflected in the production cycle of electricity. A new technology and welding consumables have been proposed for repair and restoration works of hydroelectric units at hydroelectric power plants, providing an increase in the quality level, high characteristics of hydroabrasive and cavitation resistance, and increasing of working period of hydroelectric power plants. Inspection of the body of the hydraulic unit was carried out, defects were identified and classified, the reasons for their occurrence were analyzed. The research results make possible to optimize the alloying system of the deposited metal, to determine the optimal welding mode, to reduce the amount of the martensite component and to develop new filler materials and the technology for welding and repair works of hydroelectric power plants.