Materials Science Forum Vol. 1180

Abstract: This study characterized Lygodium circinnatum (Nito), a natural fiber native to the Philippines, using a factorial design of experiments to determine the optimal alkali treatment for enhancing its chemical and mechanical properties. Sodium hydroxide (NaOH) was applied at varying concentrations (2%, 8.5%, and 15%) and soaking times, with conditions evaluated using Minitab 18 software. X-ray diffraction (XRD) was used to assess crystallinity index (CI), identifying 2% NaOH and 0.50-hour soaking as the most effective combination, yielding the highest CI. Fourier transform infrared (FTIR) spectroscopy confirmed a reduction in non-cellulosic compounds after treatment. Morphological changes were observed using scanning electron microscopy (SEM), which revealed smoother surfaces and reduced impurities. Mechanical tests showed increased tensile strength and tensile force, although a slight decrease in cross-sectional area was noted, attributed to the loss of surface material. These results demonstrate that mild alkali treatment significantly improves Nito fiber's structural integrity and performance. The study provides a scientific basis for optimizing natural fiber treatment and highlights the potential of Nito fiber in developing sustainable, high-performance materials for use in various engineering and industrial applications, including composites and biodegradable products.

Abstract: In this paper we present comparative study of frequency dependencies of an effective nonlinear elastic modulus of the three widely used glassy polymers, polystyrene, PMMA and polycarbonate. For measurements we use the methodology based on the acousto-elastic effect and analysis of variations in ultrasonic wave velocities under static stress applied to samples. The absolute values of the effective modulus γ = l − 2m, representing a combination of the Murnaghan moduli l and m, demonstrated pronounced nonlinear dependencies on the ultrasonic wave frequency for polystyrene and PMMA. At higher frequencies above ∼1 MHz no significant variations of the modulus occurred, while at lower frequencies down to 400 kHz its absolute value demonstrated a rapid rise of more than an order of magnitude. In polycarbonate the dependence was much less evident, the modulus γ also demonstrated some slight rise in the absolute value at lower frequencies, but the rise was not profound, less than two-fold and almost within the experimental error bars. The origin of the differences in nonlinear elastic properties of polystyrene/PMMA and polycarbonate requires further and more detailed investigation.

Abstract: The conditions and mechanisms of the formation of structural microstriations and their effect on the optical uniformity of undoped and doped sapphire grown by various melt methods were investigated. It was found that the striations are mainly oriented parallel to the (0001) plane and their formation do not depend on the distribution or concentration of the dopant nor on the crystallographic direction of crystal growth. The existence of spatially ordered structures in crystals, which are characterized by the formation of periodic macrostriations or "pack" with a thin internal substructure, is shown. It was found that formation of "pack" leads to the optical inhomogeneity (WFD) with an amplitude up to PV ~ λ/4 (~ 633 nm), as well as the splitting of the diffraction reflection curve (reflection <30-30>) >) into several subpeaks, which indicates the presence of polygonal dislocation boundaries with misorientation angles ~1.5''-2.0''.

Abstract: The work is devoted to a fundamental study of the magnetic properties of dilute magnetic semiconductors (DMSs). Cubic Sn_1-x-ySi_xMn_yTe (A⁴B⁶) and hexagonal layered In_1-xMn_xSe (A³B⁶) were studied. Analysis of the temperature dependencies of dynamic magnetic susceptibility by fitting with Gaussian curves revealed four universal types of cluster magnetic subsystems (CMSs) in both DMSs, regardless of their crystal structure and the main mechanism of exchange interaction (RKKY in A⁴B⁶ or Kramers in A³B⁶). It is assumed that CMSs are formed by dynamic magnetic clusters (DMCs), whose structure and dimensionality (0D, 1D, 2D, and 3D) are determined by localized vibrational modes (LVMs) and the maximum range of thermal vibrations of Mn ions, which gives them the character of quasistationary formations similar to standing waves. Each CMS is characterized by a set of five critical temperatures (T_F, T_C, Θ, T_K, β), of which T_K and β are introduced for the first time as analogues of T_C and Θ in the region of spin and cluster glasses. This approach made it possible to reveal a symmetry between two types of magnetic disorder: "overheated" paramagnetic (PM) and "supercooled" spin-glass and cluster-glass. The overlap of Gaussian curves corresponding to different CMSs explains the coexistence of spin glass (SG), cluster glass (CG), and ferromagnetic (FM) phases, which we previously observed in Ge_1-x-ySn_xMn_yTe (A⁴B⁶). The effect of annealing on the rearrangement of magnetic subsystems in In_1-xMn_xSe is shown. The concept of integral magnetic susceptibility (IMS) is introduced as a useful tool for the quantitative study of CMSs dynamics. The idea of the possibility of co-using ordered (FM) and disordered magnetic phases (SG and CG) in new functional materials for spintronics is put forward.

Abstract: The nucleation of dislocations in sapphire of various structural perfection has been investigated by nanoindentation. The studies were carried out on crystallographic planes С(0001), a(1 1 2 0), R (0 112). In the curve of indentation of a Berkovich indenter into the single crystals, an abrupt transition from elastic to plastic deformation has been observed at a depth of about 75 nm due to the nucleation of dislocations in the initially dislocation free region under the contact. Deterioration of structural perfection results in a decrease in shear stresses under which dislocations nucleated. It is shown that the anisotropy of sapphire nanohardness is less pronounced than the static one.

Abstract: Archaeometallurgical copper-artefacts contain a wide variety of metal admixtures (e.g. Pb, Bi, As, Sb, Sn) which either originate from the ores or were intentionally added. When the melt solidifies, these elements can accumulate in different structural areas and form special phases. The different alloying elements also interact with each other. In order to be able to examine these interactions, model alloys with different elements (Pb, Bi, As, Sb, Sn) and concentrations (5 or 10 wt.% each) were produced. More simple alloys show a dendritic microstructure and the added elements accumulate in the interdendritic areas. This is clearly visible for Pb and Bi additions, as both metals are not soluble in copper. As and Sb form compounds with Cu which precipitate mainly in the interdendritic regions. Sn is soluble in Cu at lower concentrations and Cu-Sn phases are formed only at higher concentrations. The resulting microstructures become very complex if more elements are involved. Finally, they enable us to have a better understanding for microstructures of ancient copper alloys.

Abstract: In the region of Inzersdorf ob der Traisen in Lower Austria, 273 cremation graves from the late Bronze Age (ca. 1300–800 BC) were recovered. Also, various bronze artefacts were found in some graves, including a button which was analyzed by metallography. It should be determined how the button was manufactured, for example by casting or soldering, and microstructural changes can be detected due to temperature effects by cremation. The button is made of bronze whose composition was determined by XRF: 87 wt.% Cu, 9 wt.% Sn and 1 wt.% Pb. The microstructure of the bronze clearly shows a temperature influence during cremation. The bronze microstructure is recrystallized as well as parts were melted, causing oxidation at the grain boundaries. Also, some areas of the bronze show small shrink holes. Further corrosion took place during long-term storage of the button in the soil.

Abstract: Several Roman bronze objects were confiscated from a digger, which had been collected illegally at the archaeological site of Burg, Burgenland. Since these parts are archaeologically worthless, they were allowed to be examined with destructive analysis methods. The investigative results of five parts are presented. The surface of the parts is covered with a green patina which contains mainly Cu and smaller amounts of Sn, Pb, P, Ca, Al, S and Fe. If XRF analyses are performed, it must be taken into account that elements such as Sn accumulate in the patina. The average XRF analyses of the hook showed a content of 0.8 wt.% Sn and about 2 wt.% Pb, but in the fibular parts and the button up to 42 wt.% Pb were detected. Due to very different compositions of the samples, the microstructures are also appropriate miscellaneous. It is possible to distinguish between cast, recrystallized and deformed microstructures. These investigations show that the Roman metallurgist used a wide variety of copper alloys, because raw and recycled materials were probably processed together.

Abstract: This study evaluated the combined effect of recycled glass powder (RGP) and nanosilica on the fresh-state properties of concrete. Mixtures were prepared with partial cement replacements of 10%, 15%, and 20%, incorporating nanosilica at 1.5 % by cement weight. The control mixture (RGP-0) does not include nanosilica, allowing comparison with the additive-containing mixtures. Results showed that RGP-10 improved workability, achieving a slump of 22.6 cm compared to 7.0 cm for RGP-0, while RGP-15 and RGP-20 exhibited only slight reductions in fluidity. Air content decreased in RGP-10, RGP-15, and RGP-20, with values of 1.6 %, 1.9 %, and 1.7 %, respectively, compared to 2.3 % in RGP-0, indicating that the mixtures with RGP and nanosilica develop a denser matrix with reduced void formation. Additionally, nanosilica accelerated early hydration, raising the initial temperature by up to 3.5 °C in RGP-20 without affecting workability. These findings demonstrate that moderate cement replacement with RGP and nanosilica can produce more stable, homogeneous, and sustainable concretes, providing useful insights for designing mixtures with improved fresh state performance.