Structural segregation in GSR from mercuric primers. A preliminary study

Since the second half of the XX century, primer mixtures based on mercury fulminate have become a rare occurrence on small ammunition markets in Western Europe and North America. As a consequence, Hg-containing gunshot residue (GSR) particles have not been as deeply investigated as residues from lead-based primer mixtures. As a matter of fact, no mention of GSR particles from mercuric primers is made by the current ASTM standard procedure for gunshot residue analysis. However, those laboratories dealing with ammunition and firearms produced in Eastern Europe or Asia still have a forensic interest in Hg-containing GSR. In this paper, a brief description of chemical composition and inner morphology of GSR particles from three different mercuric primers is reported. Regarding composition, arguments are given to promote SbSnHg residues to Characteristic of GSR particles when mercuric primers are discharged. From a morphological point of view, presence of inner nodules and other inhomogeneities were shown in GSR particles milled in a FIB/SEM. Moreover, mercury vaporization under the electron beam was observed for a particle reduced to a lamella. Mercury evanescence in GSR was interpreted in terms of mercury segregation during particle formation and higher mobility of Hg atoms in presence of defects (vacancies) in a strained lattice.

A Methodology for Multivariate Investigation on the Effect of Acrylate Molecular Structure on the Mechanical Properties and Delivery Efficiency of Microcapsules via In Situ Polymerization

In the field of encapsulation, microcapsules containing perfume have emerged as effective vehicles for delivering active ingredients across various applications. The present study employed a multivariate analysis framework to examine polyacrylate microcapsules for household products synthesized using different acrylate monomers. The advanced multivariate approach allowed us to quantify critical properties such as the Molecular Weight between Cross-links (MWc), mechanical attributes, Encapsulation Efficiency (EE), and On-Fabric delivery. It is worth noting that the mechanical properties were gauged using a novel nanoindentation technique, which measures the Rupture Force per unit diameter (RFD). Both Encapsulation Efficiency and On-Fabric delivery were assessed using GC-MS. Our findings identified the optimal microcapsule system as one synthesized with 100% aromatic hexafunctional urethane acrylate, showcasing a 94.3% Encapsulation Efficiency and an optimal RFD of 85 N/mm. This system achieved an exemplary On-Fabric delivery rate of 307.5 nmol/L. In summary, this research provides crucial insights for customizing microcapsule design to achieve peak delivery efficiency. Furthermore, by designing acrylic monomers appropriately, there is potential to reduce the amount of active ingredients used, owing to enhanced delivery efficiency and the optimization of other microcapsule properties. Such advancements pave the way for more environmentally friendly and sustainable production processes in the fast-moving consumer goods industry.

A Nanoindentation Approach for Time-Dependent Evaluation of Surface Free Energy in Micro- and Nano-Structured Titanium

Surface free energy (SFE) of titanium surfaces plays a significant role in tissue engineering, as it affects the effectiveness and long-term stability of both active coatings and functionalization and the establishment of strong bonds to the newly growing bone. A new contact–mechanics methodology based on high-resolution non-destructive elastic contacting nanoindentation is applied here to study SFE of micro- and nano-structured titanium surfaces, right after their preparation and as a function of exposure to air. The effectiveness of different surface treatments in enhancing SFE is assessed. A time-dependent decay of SFE within a few hours is observed, with kinetics related to the sample preparation. The fast, non-destructive method adopted allowed for SFE measurements in very hydrophilic conditions, establishing a reliable comparison between surfaces with different properties.

Influence of the Silver Content on Mechanical Properties of Ti-Cu-Ag Thin Films

In this work, the ternary titanium, copper, and silver (Ti-Cu-Ag) system is investigated as a potential candidate for the production of mechanically robust biomedical thin films. The coatings are produced by physical vapor deposition—magnetron sputtering (MS-PVD). The composite thin films are deposited on a silicon (100) substrate. The ratio between Ti and Cu was approximately kept one, with the variation of the Ag content between 10 and 35 at.%, while the power on the targets is changed during each deposition to get the desired Ag content. Thin film characterization is performed by X-ray diffraction (XRD), nanoindentation (modulus and hardness), to quantitatively evaluate the scratch adhesion, and atomic force microscopy to determine the surface topography. The residual stresses are measured by focused ion beam and digital image correlation method (FIB-DIC). The produced Ti-Cu-Ag thin films appear to be smooth, uniformly thick, and exhibit amorphous structure for the Ag contents lower than 25 at.%, with a transition to partially crystalline structure for higher Ag concentrations. The Ti-Cu control film shows higher values of 124.5 GPa and 7.85 GPa for modulus and hardness, respectively. There is a clear trend of continuous decrease in the modulus and hardness with the increase of Ag content, as lowest value of 105.5 GPa and 6 GPa for 35 at.% Ag containing thin films. In particular, a transition from the compressive (−36.5 MPa) to tensile residual stresses between 229 MPa and 288 MPa are observed with an increasing Ag content. The obtained results suggest that the Ag concentration should not exceed 25 at.%, in order to avoid an excessive reduction of the modulus and hardness with maintaining (at the same time) the potential for an increase of the antibacterial properties. In summary, Ti-Cu-Ag thin films shows characteristic mechanical properties that can be used to improve the properties of biomedical implants such as Ti-alloys and stainless steel.

FIB/SEM and SEM/EDS microstructural analysis of metal-ceramic and zirconia-ceramic interfaces

Recently introduced FIB/SEM analysis in microscopy seems to provide a high-resolution characterization of the samples by 3D (FIB) cross-sectioning and (SEM) high resolution imaging. The aim of this study was to apply the FIB/SEM and SEM/EDS analysis to the interfaces of a metal-ceramic vs. two zirconia-ceramic systems. Plate samples of three different prosthetic systems were prepared in the dental lab following the manufacturers' instructions, where metal-ceramic was the result of a ceramic veneering (porcelain-fused-to-metal) and the two zirconia-ceramic systems were produced by the dedicated CAD-CAM procedures of the zirconia cores (both with final sintering) and then veneered by layered or heat pressed ceramics. In a FIB/SEM equipment (also called DualBeam), a thin layer of platinum (1 μm) was deposited on samples surface crossing the interfaces, in order to protect them during milling. Then, increasingly deeper trenches were milled by a focused ion beam, first using a relatively higher and later using a lower ion current (from 9 nA to 0.28 nA, 30KV). Finally, FEG-SEM (5KV) micrographs (1000-50,000X) were acquired. In a SEM the analysis of the morphology and internal microstructure was performed by 13KV secondary and backscattered electrons signals (in all the samples). The compositional maps were then performed by EDS probe only in the metal-ceramic system (20kV). Despite the presence of many voids in all the ceramic layers, it was possible to identify: (1) the grain structures of the metallic and zirconia substrates, (2) the thin oxide layer at the metal-ceramic interface and its interactions with the first ceramic layer (wash technique), (3) the roughness of the two different zirconia cores and their interactions with the ceramic interface, where the presence of zirconia grains in the ceramic layer was reported in two system possibly due to sandblasting before ceramic firing.

Surface analysis and osteoblasts response of a titanium oxi-carbide film deposited on titanium by ion plating plasma assisted (IPPA)

Titanium is the most widely used material in orthopaedic and dental implantoprosthesis due to its superior physical properties and enhanced biocompatibility due to the spontaneous formation of a passivating layer of titanium oxides which, however, does not form good chemical bonds with bone and tends to brake exposing bulk titanium to harsh body fluids releasing titanium particles which may prime an inflammation response and a fibrotic tissue production. In order to avoid these possible problems and to enhance the biocompatibility of titanium implants, modifications of titanium surfaces by many different materials as hydroxyapatite, titanium nitride, titanium oxide and titanium carbide have been proposed. The latter is shown to be an efficient protection for the titanium implant in the harsh conditions of biological tissues and, compared to untreated titanium, acting like an osteoblast stimulation factor increasing in vitro production of proteins involved in osteogenesis. These results were confirmed by in vivo experiments in rabbits: implants covered by the titanium carbide (TiC) layer were faster and better osseointegrated than untreated titanium implants. The TiC layer was deposited by a Pulsed Laser Deposition (PLD) device which allowed only one deposition per cycle, shown to be unsuitable for industrial applications. Therefore the main objective of the present work was to replace PLD process with an Ion Plating Plasma Assisted (IPPA) deposition process, which is suitable for industrial upgrading. By this technique, nanostructured TiOx-TiCy-C has been deposited on titanium after sandblasting with 120 micron zirconia spheres. XPS analyses revealed the presence of about 33% carbon (50% of which is present as free carbon), 39% oxygen and 28% titanium (37% of which is bound to carbon to form TiC and 63% is bound to oxygen to form non stoichiometric oxides). Surface mechanical response of as-deposited coatings has been performed by nanoindentation techniques. Focused Ion Beam micrographs showed bigger differences on the obtained nanostructure compared to the PLD coating structure; in vitro tests confirm for IPPA produced coatings an improvement in stimulating osteoblasts to produce mRNA's of proteins involved in the ossification process, this latter case they resulted to be faster and more efficient. The proposed treatement is expected to improve the good results obtained by PLD, in vivo as well.

On the influence of residual stress on nano-mechanical characterization of thin coatings

In the present paper, the effect of residual stress on the mechanical behavior of thin hard coatings has been investigated by a new methodology based on the combined use of focused ion beam (FIB) micro-machining techniques and nanoindentation testing. Surface elastic residual stress were determined by nanoindentation testing on Focused Ion Beam (FIB) milled micro-pillars. The average residual stress present in a 3.8 microm CAE-PVD TiN coating on WC-Co substrate was calculated by the comparison of two different sets of load-depth curves, the first one obtained at centre of stress relieved pillars, the second one on the undisturbed (residually stressed) surface. Results for stress measurement were in good agreement with the estimate obtained by XRD (sin2 psi method) analysis on the same sample, adopting the same elastic constants. In addition, nanoindentation on stress relieved pillars also allowed to perform a more accurate evaluation of elastic modulus and hardness of the coating. The effect of residual stress on crack propagation modes was quantitatively analyzed by high-load nanoindentation and application of energy methods for fracture toughness evaluation. It is found that compressive residual stress plays a relevant role in determining the fracture behavior and failure modes of the coating. Finally, Microstructural observations of the deformation mechanisms of the TiN coating were performed by TEM analysis on the cross section of the indentation, obtained by FIB lamella thinning. Results showed that plastic deformation at the nanoscale essentially occurs by formation of shear bands inside the columnar grains, independently of residual stress. A transition between intra-granular shear deformation and columnar grain sliding is also observed as a function of the applied load.

Filler-matrix interaction in solid-state foaming of composite foams

Solid-state foaming is a relatively new process for producing closed-cell thermoset foams starting from powders. In this study, the possibility of introducing nanoclay into epoxy foams by solid-state foaming was investigated. The nanoclay was found to affect the foaming efficiency and the foam density; even if large nanoclay aggregates are present in the foams, for a small range of filler content (2.5—3 wt%), the mechanical properties are positively influenced, as shown by specific compressive toughness which attains a maximum value. Electron microscope observations provided important information on the dependence of the cell size on the filler percentage, and the presence of a critical size (about 5 μm) of nanoclay aggregates, below which they are coherent with the matrix.

Verification of Layered Structures in SnO2/Metal-based Gas Sensors by X-ray Microanalysis: Comparison with X-ray Photoelectron Spectroscopy

The depth profile of thin film layers on bulk substrate, avoiding the cross-sectioning of samples, is commonly performed by techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectroscopy (SIMS). Techniques based on X-ray emission intensity measurements by energy dispersive spectroscopy (EDS), with conventional matrix or ZAF correction, are normally applied to cross-sectioned samples. This article compares XPS with surface X-ray intensity measurements by EDS, carried out with a more realistic X-ray generation and absorption model, known as the pi(rho Z) model. The pi(rho Z) approach has been adopted together with Monte Carlo simulation for the proper selection of SEM accelerating voltages, in conjunction with the analysis of SEM morphological images for thin film density correction. The method discussed hereafter and compared with the XPS technique, has advantages of higher lateral resolution, non-destructive elemental analyses, morphological visualization, low cost, and faster performance. This methodology has been followed to verify the layered structure of SnO2/metal-based gas sensors. X-ray intensities were measured using an EDS ultra-thin window detector. Two different porous layers, 25-nm thick of SnO2 and 10-nm thick of Cu, were detected, showing better agreement with their nominal thickness compared to results obtained using XPS measurements where porosity affects XPS data. If confirmed to be reliable and as effective as XPS depth profiling, this technique may be adopted for process quality control purposes.

Tensile experiments and SEM fractography on bovine subchondral bone

Subchondral bone undecalcified samples, extracted from bovine femoral heads, are subjected to a direct tensile load. The Young's modulus of each sample is determined from repeated tests within the elastic limit. In a last test, the tensile load is increased up to the specimen failure, determining the ultimate tensile strength. The investigation is performed on both dry and wet specimens. The measured Young's modulus for dry samples is 10.3+/-2.5GPa, while that of wet samples is 3.5+/-1.2GPa. The ultimate tensile strengths are 36+/-10 and 30+/-7.5MPa for dry and wet specimens, respectively. SEM micrographs of failure surfaces show characteristic lamellar bone structures, with lamellae composed of calcified collagen fibers. Rudimentary osteon-like structures are also observed. Failure surfaces of wet samples show a marked fiber pull-out, while delamination predominates in dry samples. The obtained results are interpreted on the basis of the deformation mechanisms typical of fiber-reinforced laminated composite materials.