The TiCxN1−x (0≤x≤1) is widely used in wear-resistant and high-temperature coatings, where a precise understanding of its thermal expansion behavior is essential to prevent delamination, cracking, and thermal fatigue during service. Although several studies have examined its thermal expansion, reported values vary significantly depending on measurement conditions and composition. This work integrates high-temperature X-ray diffraction (HT-XRD) experiments and molecular dynamics (MD) simulations to determine the thermal expansion of TiCxN1−x between 300 and 2500 K. The lattice parameter was fitted as a function of temperature using linear and quadratic polynomials to extract reliable thermal expansion coefficients. The MD-derived linear thermal expansion coefficients agree within 3% of experimental trends, confirming the accuracy of the simulations for predicting first-order thermal behavior. While second-order terms deviated by up to 59%, their contribution to the overall expansion was negligible. Simplified linear expressions for the lattice parameter (a) and average thermal expansion coefficient (αav) are thus reported as explicit functions of temperature and composition. These results provide practical equations for the design and thermal matching of TiCxN1−x coatings with metallic or ceramic substrates, enabling improved durability in cutting tools, thermal barrier coatings, and other high-temperature mechanical applications. The combined experimental–computational approach demonstrates a rapid and transferable methodology for optimizing thermomechanical performance in advanced nitride–carbide materials and TiCxN(1−x) coated diamond tools.

New potential parameters for the Ti-C-N ternary system based on the second nearest neighbor modified embedded atom method (2NN MEAM) are reported. The parameters were developed starting from published binary systems for Ti-C and Ti-N and fitted using published data of lattice constants, formation enthalpy, bulk modulus, elastic constants, and surface properties for several C/N ratios in the cubic B1 structure. The simulated systems using the new parameters show agreement with structural and elastic experimental and first-principles values. Our results highlight novel methods to calculate several mechanical and thermal properties of TiCxN1−x systems.

Heat treatments are frequently used to modify the microstructure and mechanical properties of materials according to the requirements of their applications. Laser surface treatment (LST) has become a relevant technique due to the high control of the parameters and localization involved in surface modification. It allows for the rapid transformation of the microstructure near the surface, resulting in minimal distortion of the workpiece bulk. LST encompasses, in turn, laser surface melting and laser surface hardening techniques. Many of the works devoted to studying the effects of LST in cast iron are diverse and spread in several scientific communities. This work aims to review the main experimental aspects involved in the LST treatment of four cast-iron groups: gray (lamellar) cast iron, pearlitic ductile (nodular) iron, austempered ductile iron, and ferritic ductile iron. The effects of key experimental parameters, such as laser power, scanning velocity, and interaction time, on the microstructure, composition, hardness, and wear are presented, discussed, and overviewed. Finally, we highlight the main scientific and technological challenges regarding LST applied to cast irons.

Copper is a metal well known for its antimicrobial properties. However, copper-made structures such as pipes and clinical supplies are prone to be colonized by copper-tolerant bacteria. Recent works have shown that modifications of the topography and surface chemistry of metals using direct laser interference patterning (DLIP) affect bacterial settlement. In this work, DLIP was used to texture copper surfaces with parallel line patterns on the size scale of a bacterium. The effects of texturing on the copper surface were characterized by scanning electron microscopy, atomic force microscopy, contact angle and corrosion analyses, and X-ray photoelectron spectroscopy. The antimicrobial properties were assessed by using the live/dead test. Experiments were performed on both the copper-tolerant bacterium Variovorax sp. and the noncopper-resistant bacterium Escherichia coli . Our results indicate that although the increase in Cu(OH) 2 might influence the toxicity of the surface, the controlling factor of the antimicrobial activity of laser-textured copper surfaces is the contact area per bacterium. This work highlights the application of laser texturing technologies to enhance the antimicrobial behavior of metals.

The aim of this work is the analysis of laser beam forming (LBF) in the bending of two relevant materials used in the transportation industry—interstitial-free (IF) steel and AA6013 high-strength aluminum alloy. Our experiments and numerical simulations consider two different operating scenarios achieved by varying the laser beam scanning velocity using linear paths. The material behavior during this process is described via a coupled thermomechanical-plasticity-based formulation that allows prediction of temperature profiles and bending angles. Metallography, glow discharge optical emission spectroscopy, and X-ray diffraction are used for microstructure characterization. In addition, microstress analyses are performed in order to study the stress behavior of the irradiated zones. It is found that LBF mainly induces grain growth and melting in the case of high surface temperatures. Before melting, the materials developed compressive stresses that could be useful in preventing cracking failures. The resulting bending angles are predicted and experimentally validated, indicating the robustness of the model to estimate LBF effects on advanced alloys. The present analysis relating bending angles together with temperature and microstructure profiles along the thickness of the sheets is the main original contribution of this work, highlighting the need for further modeling refinement of the effects of LBF on advanced alloys to include more microstructural properties, such as grain boundary diffusion and surface roughness.

Surface transformation treatments like laser surface melting and laser surface hardening have been mostly developed in austempered ductile iron and gray cast iron. In this work, we explore the effects of the linear laser energy of the treatment on the microstructure, chemical composition, and hardness of ferritic nodular cast iron, using a fiber delivery diode laser. We found changes in the microstructure above 120 J/mm, characterized by the presence of graphite nodules surrounded by martensitic/dendritic shells. Above 316 J/mm, Fe3C and γ-Fe2O3 phases arise, together with a saturation of the microhardness around 1000 HV0.3 within the first 200 μm of depth, and of the surface hardness around 90 HR15N. Changes in microstructure and composition due to the laser treatment directly affect the thermal diffusion between the surface-modified zones and the nodular cast iron bulk. Our work highlights the importance of the linear energy in the design and planning of laser treatments.

The growth of detrimental biofilms on metal surfaces affects their structural performance and lifespan. Microtopographic texturization has emerged as an approach to suppress biofilm growth by preventing the initial stages of bacterial adhesion. This work studies the effects of linear pattern copper texturization on the initial adhesion steps of the biofilm-forming and copper-resistant bacterium Variovorax sp. Linear patterns with 4.7, 6.8, 14, and 18 μm periodicity were produced by direct laser interference patterning (DLIP) on copper coupons. Surface features were characterized by microscopic and spectroscopic techniques, and bacterial adhesion behavior was characterized by epifluorescence microscopy and functionalization of atomic force microscopy tips. We found a periodicity of 4.7 μm as the most efficient pattern to suppress Variovorax sp. initial adhesion by 31.1 % with respect to the nontextured surface. Preferential settlement in hummocks over hollows was observed for patterns with 14 and 18 μm periodicity, with adhesion events showing higher frequency in these topographies than patterns with periodicities of 4.7 and 6.8 μm. Our results highlight an understanding of the initial bacteria-copper adhesion and settlement behavior, thus contributing to the potential development of innocuous strategies for controlling biofilm growth on copper-based materials.

The thermal behavior of MoO3-nanostructures is relevant for the design of tribological additives containing Mo-oxides. We report on thermal behavior of porous MoO3-nanostructures analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The nanostructures were grown by gas condensation under H-2. Our results revealed 3 stages of phases behavior as a function of temperature. We found dehydration of MoO3-0,33 H2O after 180 degrees C followed by the formation of beta-MoO3 after 230 degrees C, then to alpha-MoO3 after 280 degrees C, and finally formation of suboxide gamma-Mo4O11 at similar to 330 degrees C. The formation of the latter is mainly due to the crystallization and reduction of the porous oxide matrix. Our results highlight that both thermal and chemical processes must be taken into account when designing tribological additives that contain MoO3. (C) 2021 Elsevier B.V. All rights reserved.

In this work, growth, characterization and thermo-mechanical behavior of Al/Al2O3 core/shell nanoparticles (NP) is performed. The growth was carried out by gas condensation methods using H-2 as carrier gas at a pressure of 100 Pa and with a temperature of the evaporation source of 1315 degrees C. The prepared NP were characterized by Energy Dispersive X-ray Spectroscopy for chemical information, transmission electron microscopy for morphological study, and electron diffraction patterns for structural information. The prepared Al NP exhibit a thin Al2O3 passivating oxide shell due to the air exposure when removed from the preparation vacuum chamber. Afterwards, the growth of the Al2O3 oxide shell of the Al NP and the thermo-mechanical interaction between this growing oxide shell and its Al core was studied by performing in-situ thermal X-ray diffraction from RT up to 505 degrees C. Coefficients of thermal expansion of both Al core and Al2O3 oxide shell were obtained by means of X-ray strain analysis. It was found that the thickness of the Al2O3 shell increases with temperature and the thermal stress induced in the system increases linearly with temperature. Our results highlight that these NP overcome higher values of fracture toughness compared with Al2O3 NP used in micro-nano composites, thus improving their mechanical properties for nanofluid applications.

We present the results of a study of Chilean students' understanding of scientific models, using a Spanish-adapted version of the Students' Understanding of Models in Science instrument (Treagust, D. F., Chittleborough, G., & Mamiala, T. L. (2002). Students understanding of the role of scientific models in learning science. International Journal of Science Education, 24(4), 357-368. doi:10.1080/09500690110066485). The study covered 290 students in three schools in different parts of Chile. Results showed a Cronbach's alpha of 0.86 and medium correlation between the dimensions of the instrument. A confirmatory factor analysis showed that the five dimensions' theoretical structure is supported by the data, and one-way ANOVA and a t-test showed a balanced, non-discriminatory instrument that is suited for use in the Spanish language. The instrument also showed that Chilean students most need improvement in two of the dimensions - 'understanding of scientific models in terms of exact replicas' and the 'use of scientific models'. This reflects the original data analysed by Treagust et al. (2002) and suggests that these factors are common issues in the teaching and learning of scientific models. Future research will review the data by year and group to determine how students develop the idea of a scientific model and relate this information to science curricula. It will also investigate the link between students' understanding of scientific models and Anderson & Krathwohl's (2001) cognitive taxonomy.

The ever more diverse applications of carbon materials require new fabrication methods to satisfy the demand of functionalization. This work seeks extending functionality of carbon foams known to be determined by their porous properties, which in turn are mainly produced during synthesis. In this work, we report a simple and versatile method to produce hierarchical mesoporous carbon with bottom-up grown crystalline ZnO coating obtained in one pot. The synthesis is based on foaming xylene-epoxy-zinc suspensions, which are further subjected to carbonizing treatments. Two carbon foams carbonized at high (1000 degrees C) and low (500 degrees C) temperatures are compared. During carbonization, zinc particles were found to diffuse towards the foam's surface and evaporate in case of the high temperature process, whereas reaction to form the crystalline ZnO coating was found in the low temperature process. The surface area and pore volume of the carbon foams depend on the Carbonizing temperature due to the direct relation with the diffusion rate of particles in the material. This also explains the formation of the oxide layer at the foam external surface observed in the low temperature treatment. This work highlights the possibilities of improving the functionality of porous carbon materials by adding ceramic coatings.

The performance of perovskite films in capacitor devices is strongly determined by the level of residual stresses developed after their fabrication at high temperatures. Quantification of these stresses by X-ray diffraction is not straightforward in perovskite films due to the complexity of the crystalline structure and a lack of effective elastic diffraction constants. In this work we apply a simple and accurate method to estimate the residual stresses developed in Pb(Nb,Zr,Ti)O3 perovskite films grown by metal–organic chemical vapor deposition on the Pt electrode. The stress was directly measured in the Pt bottom electrode film before and after the deposition of the perovskite film and compared with intrinsic and thermal stresses calculations. Our results reveal in-plane tensile stresses of 676(8) MPa developed in the Pt electrode, which mainly originate from the relative thermal contraction between Pb(Nb,Zr,Ti)O3 and Pt as well as the cubic-tetragonal perovskite phase transformation after deposition. This methodology is straightforward and highlights the possibility to perform systematic studying for tailoring stress conditions and improving the performance of perovskite films for capacitor applications.

Properties of poly(binaphthoxyphosphazene)s were investigated employing molecular dynamics simulations in the original microcanonical ensemble. In particular we have applied our methodology to the case of isotactic poly-(2,2´-dioxy-1,1´-binaphthylphosphazene) (P-DBNP) in order to estimate the vitreous transition temperature Tg, the energy barrier Δμβ for β-relaxation of the BNP unit, and the thermodynamic entropy of the system. According to our results, the transition is consistent with the Adam-Gibbs model and the specific rotation of α and β-relaxations, which varies significantly with the molecular weight Mw. Our results suggest a rapid interconversion between the different proportions of the chiral R and S repeating units (70% and 30%, respectively) of the non-isotactic copolymer below 523K and a slow atropisomerization of the DBNP units above 523K which, in agreement with recent predictions on glassy polymer matrices, becomes much faster as the temperature approaches Tg~573K.

Increasing demands on modern connector materials for automotive applications, driven by the trends in miniaturization and electrification, require higher operating temperatures and lower contact normal loads. These lead to increased wear, begging the need for upgraded connector materials. In order to improve the electrical and wear behavior of an existing surface finish, the use of direct laser interference patterning (DLIP) on tin-plated copper contacts is explored. The focus of this paper lies on the evolution of the electrical resistance between textured contacts and a probe with an inert coating under normal loading. The microstructural and topographical changes due to DLIP as well as indentation during the contact resistance measurement are investigated by white light interferometry, scanning electron microscopy, and focused ion beam. The patterns change the primary deformation mechanism of the connector surface, which facilitates the fracture of electrically insulating oxide layers. This in turn leads to a decreased contact resistance in the considered load range, compared to the nontextured samples.

Purpose The purpose of this paper is to explore the possibility of producing Cu-based shape memory alloys (SMA) by means of direct metal laser fabrication (DMLF). Design/methodology/approach The fabrication approach consists of the combination of laser melting of a metallic powder with heating treatment in a controlled inert atmosphere. Three prospective Cu-Al-Ni alloy compositions were tested, and the effects of laser power, as well as laser exposure time, were verified. Findings All the processed materials were found to attain microstructures and phase change transformation temperatures typical of this type of SMA. Practical implications Further development of this technique will allow for fabrication of large elements with considerable shape memory effect, which are currently not viable due to high cost of nitinol. Originality/value This work showed a proof of concept toward the development of DMLF-based additive manufacturing of near net shape components of Cu-based SMAs from elemental powders.

Decorating carbon nanotubes (CNTs) with nanoparticles has proved to be an intelligent approach to improve the gas adsorption properties of CNTs for the development of new sensors, including hydrogen sensors. However, in order to take advantage of this hybrid structure, methods are needed that ensure a proper decoration and the fabrication of small features without compromising the sensing surface. Within this paper, we report a novel technique to simultaneously decorate multiwall carbon nanotubes (MWCNTs) with gold–palladium nanoparticles and transfer them to a substrate by laser-induced forward transfer using femtosecond laser pulses. The nanoparticles decorating the MWCNTs present a spherical shape with a Feret diameter bellow 200 nm. The nanoparticle size can be tuned by varying the amount of pulses within the transfer. Finally, hydrogen adsorption showed up to a 20-fold increase compared to a sample composed of non-transferred, non-decorated MWCNTs.

This work presents the analysis of a fractured impeller used in slurry pumps at the Collahuasi copper mine in Chile. Although the impeller must run more than 1 800 h, it was fractured under working conditions before having reached 1 500 h, generating a catastrophic failure of the pumping system. The microstructure of the impeller material was analyzed by optical microscopy, scanning electron microscopy (SEM) and microhardness. The composition of the impeller material was studied by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Raman spectroscopy. It was found that the impeller material corresponds to cast iron with high content of chromium, typically called white cast iron, which usually exhibits high wear and corrosion resistance. After analyzing the overall failure, we conclude that the fracture was mainly produced by the existence of high-impact materials in the slurry pulp, which produced an imbalance of the impeller rotation.

For many years already, a lot of research groups try to shed light on the origin of friction and to enhance the tribological performance of rubbing surfaces. In this context, the ability to tailor the tribological properties on different scales is of utmost importance. In this work, laser interference patterning is used to produce well-defined surface topographies with line- and cross-like patterns in order to modify the tribological performance under dry and lubricated conditions. Under dry conditions, the frictional behavior of line-like patterned surfaces having a periodicity of 9 μm are investigated using a ball-on-disk tribometer in linear reciprocating sliding mode as a function of the normal load and the relative alignment. Regarding mixed lubrication, the oil film lifetime of cross-like patterns (periodicity of 9 μm) is evaluated using a ball-on-disk tribometer (normal load of 5 N and sliding velocity of 5 cm/s) in rotational sliding mode. The experiments under dry friction demonstrate a significant friction reduction for the line-like surface patterned surfaces, independent on the respective alignment. Dependent on the used normal load, differences in the frictional behavior are observed. For the cross-like patterns under mixed lubrication, an increase of the oil film lifetime by a factor of 56 is achieved.

Metallographic preparation is an art, especially when relevant information hidden at the micro-or nano-scale has to be unraveled. In particular, electron backscattered diffraction (EBSD) is a technique that provides valuable information of the microstructure of bulk and coatings. Indeed, information regarding evolution of the morphology, size and orientation of grains is very relevant for the design and fabrication of new commercial coatings. Metallographic preparation for EBSD analysis of hard coatings consisting of Al2O3 and TiCN layers is presented in this work. In particular, preparation timing during grinding and polishing is discussed. EBSD data is presented and correlated with the metallographic preparation parameters. The main conclusions of this work highlight the importance of systematic preparation of all the successive metallographic procedures and the understanding of the quality parameters associated with the EBSD scans and data processing.

We report on in-situ high temperature X-ray thermal stress analysis of chemically graded Ti(C,N) coatings deposited on functionally graded cemented carbide substrates by chemical vapor deposition. The in-situ analyses were performed by energy dispersive X-ray diffraction using synchrotron radiation. The samples were subjected to one individual thermal cycle from room temperature to 800°C and cooled down to room temperature again. The stresses were determined using the sin2ψ method in the Ψ geometry combined with scattering vector measurements in order to unravel the compositional influences on the lattice strain distributions. It was found that the Ti(C,N) thin film presents a cycling residual stress behavior (tensile–compressive–tensile) connected to the temperature cycle. If top-blasting is applied on the thin film layer after the coating process, compressive stresses are generated. These compressive stresses induced by top-blasting are partially released after the high temperature thermal cycle. The functionalization of the cemented carbide substrate influences the level of stresses developed in the coating. The stress behavior as a function of temperature is discussed with the support of finite element modeling by introducing a bi-linear plasticity model to calculate strain relationships which is in agreement with the synchrotron measurements.