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The utilization of hollow glass particle‐filled fiber‐reinforced composites in marine applications necessitates a proper understanding of their behavior when exposed to moisture environments. In this study, the glass fiber‐reinforced composites reinforced with 0%–30% volume fraction of glass microspheres were fabricated and immersed in seawater and distilled water conditions for monotonic tensile and flexural testing. The degradation mechanisms were analyzed by dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FT‐IR), and scanning electron microscopy (SEM). Moisture absorption results showed an increasing trend with the inclusion of glass microspheres. A decline in glass transition temperature and storage modulus was observed as a result of moisture absorption. The tensile results of the specimens exhibited a decrease of 13% and 9% in distilled water and seawater solution, respectively when compared with unaged samples, respectively. The flexural results of the aged composite specimens demonstrated a reduction of 24% and 11% in distilled water and seawater solution, respectively when compared with unaged samples. The findings also show that the influence of moisture on the modulus is less pronounced compared to its effect on strength under both environmental conditions. The micrograph results revealed a notable deterioration of the glass microsphere and the fiber/matrix interface in the moist environment. Highlights: Water absorption increases with the addition of glass microspheres.Microsphere degradation and fiber/matrix debonding are the governing mechanism.Retained 89% of tensile strength of their initial properties after exposed in sea water.Increase in microsphere contents decreases the tensile and flexural strength. [ABSTRACT FROM AUTHOR]

Although glass recycling is considered to be a default method for glass waste management, fine fractions of container soda‐lime glass, or cullet of other compositions are still landfilled. This happens despite existing alternatives. Success could lie in advanced upcycled products that bring higher economic motivation for the implementation in industry, but these are often connected to alternative ways of product synthesis. We provide an example of waste glass upcycling by the preparation of glass microspheres (GM) from specialty low‐sodium alumino borosilicate‐based glasses via flame synthesis (FS). GM and the precursors, either from colorless medical vials or glass fibers, were characterized by scanning electron microscopy (SEM), simultaneous thermal analysis coupled with differential thermal analysis (STA‐DTA), and image analysis. A dynamic corrosion test was performed and evaluated via ion‐coupled plasma with optical emission spectroscopy (ICP‐OES) to observe corrosion kinetics products. FS has proved to be a fast method of waste glass processing into GM. This article, besides the characterization of the starting material and final products, also suggests the possibility of processing for other landfilled waste glasses and also discusses the manufacturing of GM for water filters and fillers for polymers. [ABSTRACT FROM AUTHOR]

Glass microspheres with the exact stoichiometry of åkermanite (Ca2MgSi2O7), one of the most promising modern bioceramics, were produced by the flame synthesis method. The distinctive high cooling rate was found to prevent the crystallization; the size of amorphous microbeads could be correlated with the size of partially crystallized precursor powders, deriving from conventional melt quenching and milling. The glass microspheres were characterized in terms of crystallization and sintering behavior, in the perspective of applications in additive manufacturing of åkermanite‐based scaffolds. The results showed that merwinite (Ca3MgSi2O8) is the primary product of glass devitrification; only in a second stage, merwinite reacts with the residual glass and yields åkermanite. The rapid crystallization, implying limited viscous flow sintering, was tested as an opportunity to create components with complex porosity distribution. [ABSTRACT FROM AUTHOR]

Despite many advantages, poor mechanical properties are a limiting factor in market growth of natural fiber composites. This work is focused on improvement in the mechanical properties of hemp/green epoxy composites by using four different weave structures and by adding glass microspheres (GMS) to the resin. The reinforcement was fabricated in four different weave designs (matt, satin, hybrid weave A, and hybrid weave B) and four different percentages of GMS (0%, 2%, 3.5%, and 5% on the weight of resin) were also mixed in the green epoxy resin. Four layered composites were fabricated by using vacuum bagging technique. The tensile, flexural and impact tests were conducted. The results showed that the tensile strength of composites with satin weave reinforcement is better than other weaves, due to longer warp thread float and lesser number of intersection points. While, during flexural and pendulum (Charpy) impact testing, matt weave composite showed better results due to its stable and robust structure as compared to the other weave composites. Keeping the weave design constant, the composites with 5% GSM showed better tensile, flexural and impact behavior. Both factors (weave design and GMS percentage) showed a statistically significant effect on the mechanical test results. [ABSTRACT FROM AUTHOR]

This article features the oxidation behavior of ferritic stainless steel grade AISI 441 coated with protective polymer‐derived ceramics (PDC). Two PDC compositions are studied with respect to their oxidation resistance in a flow‐through atmosphere of synthetic air at temperatures of up to 1000°C. The coatings contain a combination of six passive fillers: Y‐containing ZrO2, glass microspheres, alumina‐yttria‐zirconia (AYZ) powder, and three commercial glasses. They are pyrolyzed in air for 1 hour at 800°C with heating and cooling rates of 3 K/min. Detailed microstructural examination of the oxide products formed at the surface of samples after exposure to air at 900°C, 950°C, and 1000°C for 1‐48 hours is analyzed. Both uncoated steel and steel coated with two of the protective systems described in part 1 of this article are investigated. Fe, Cr2O3, TiO2, and a spinel of the composition (Mn,Cr)3O4 are identified at the oxidized surface of the steel substrate using X‐ray diffraction. A significant weight gain of the unprotected steel is measured after all experiments, while oxidation tests of the coated steel show a negligible weight gain after 900°C and 950°C. During the early stages of coating oxidation, the monoclinic‐to‐tetragonal ratio in the zirconia filler is shifted toward the monoclinic modification. Longer exposures and higher temperatures lead to the formation of yttrium aluminum garnet (YAG) due to glass microsphere crystallization and solid state reactions in the AYZ powder. The crystallization of the three commercial glasses functioning as sealants leads to the formation of Ba(AlSiO4)2 also known as hexacelsian, which subsequently transforms to celsian. YZr8O14 is also formed. The protective effect of the PDC coatings applied to the stainless steel is demonstrated up to 950°C. [ABSTRACT FROM AUTHOR]

Tiny bubbles or glass microspheres/microcapsules are used in our society today in many ways. The microspheres can be solid or hollow and represent particles that are generally in the range of 0.1-100 μm. Solid and hollow microspheres have significantly different densities, properties, and capabilities and are commercially available. Special morphologies, formulations, and compositions can also be achieved by a variety of techniques in the laboratory. One of the most interesting morphologies of these tiny bubbles, are porous wall hollow glass microspheres, which are glass micro-balloons in which through-wall porosity was induced in the thin outer shells and controlled, on a scale of 10-100 nm. This unique porosity can be used to fill the microspheres with a variety of cargos of various contents that can later be released on demand. For medical applications, an interdisciplinary team investigated these tiny bubbles, as part of a new series of composites or medical cocktails. The microspheres are key components in the composites and can be used alone or mixed in various amounts and ratios, with a variety of contents, outer coatings, and/or biocompatible matrices, resulting in a wide range of medical cocktails designed and tailored for various applications. [ABSTRACT FROM AUTHOR]

Microspheres made from optical glasses such as silica and chalcogenide are used as both passive and active optical elements in micro-optics systems and devices. The homogeneity of the microspheres is crucial to their optical quality and performance in such devices and so it is essential, in optimizing such systems, that techniques with nanometer scale resolution are developed to measure the internal structure and homogeneity of such spheres. In this work an analytical protocol based on focussed ion beam milling, combined with secondary ion and secondary electron imaging, has been developed to study the internal homogeneity of glass microspheres. The results have shown that silica microspheres with diameters of three to five microns, fabricated by a sol-gel method, have internal inhomogeneities and voids that will lead to non-uniform optical properties. The FIB milling and imaging technique developed has been found to be a very useful method of studying such inhomogeneities, which have been proposed, but never previously observed, in glass microspheres. The FIB based technique has also been used on larger chalcogenide glass (Ga2S3:La2S3) microspheres (diameter of order 70 microns) but no inhomogeneities have been observed at the spatial resolution of a few microns so far achieved for these larger microspheres. This study suggests that the FIB based milling and imaging technique may have potential for quantitative use in the measurement of morphological variations in such systems as well as in the study of aging processes in micron-sized glass spheres. [ABSTRACT FROM AUTHOR]

In the present study, we tested the hypothesis that similar to other mechanical loads, notably cyclic stretch (simulating pre-load), glass microspheres simulating afterload will stimulate the secretion of angiogenic factors. Hence, we employed glass microspheres (average diameter 15.7 μm, average mass 5.2 ng) as a new method for imposing mechanical load on neonatal rat ventricular myocytes (NRVM) in culture. The collagen-coated microspheres were spread over the cultures at an estimated density of 3000 microspheres/mm2, they adhered strongly to the myocytes, and acted as small weights carried by the cells during their contraction. NRVM were exposed to either glass microspheres or to cyclic stretch, and several key angiogenic factors were measured by RT-PCR. The major findings were: (1) In contrast to other mechanical loads, such as cyclic stretch, microspheres (at 24 hrs) did not cause hypertrophy. (2) Further, in contrast to cyclic stretch, glass microspheres did not affect Cx43 expression, or the conduction velocity measured by means of the Micro-Electrode-Array system. (3) At 24 hrs, glass microspheres caused arrhythmias, probably resulting from early afterdepolarizations. (4) Glass microspheres caused the release of angiogenic factors as indicated by an increase in mRNA levels of vascular endothelial growth factor (80%), angiopoietin- 2 (60%), transforming growth factor-β (40%) and basic fibroblast growth factor (15%); these effects were comparable to those of cyclic stretch. (5) As compared with control cultures, conditioned media from cultures exposed to microspheres increased endothelial cell migration by 15% (P<0.05) and endothelial cell tube formation by 120% (P<0.05), both common assays for angiogenesis. In conclusion, based on these findings we propose that loading cardiomyocytes with glass microspheres may serve as a new in vitro model for investigating the role of mechanical forces in angiogenesis and arrhythmias. [ABSTRACT FROM AUTHOR]