Hard Solids Research Articles

Investigating the Influence of the Substrate Temperature and the Organic Precursor on the Mechanical Properties of Low‐Pressure Plasma Polymer Films

ABSTRACTThis work aims to investigate the influence of the substrate temperature on low‐pressure plasma polymerization processes. Emphasis is placed on the mechanical properties and growth mechanism of the plasma polymer films (PPFs). For this purpose, two precursors are considered, differing only by their unsaturation degree: 2‐propen‐1‐ol (CH2═CH–CH2–OH) and propan‐1‐ol (CH3–CH2–CH2–OH). Although propan‐1‐ol‐based PPFs behave like hard elastic solids, 2‐propen‐1‐ol‐based coatings evolve from a liquid film to an elastic solid on increasing the substrate temperature. This behavior is understood considering the evolution of the glass transition temperature of PPFs. The latter is correlated with the cross‐linking degree of the polymeric network governed by the energy density of bombarding ions on the growing film.

Perspective on oral processing of plant-based beverages.

Around the world, the market for plant-derived beverages is one of the fastest-expanding segments in the functional and specialty beverage areas of newer food product development. Consumers are increasingly likely to choose alternatives to bovine beverages due to factors including lactose intolerance, hypercholesterolemia prevalence, allergies to bovine beverages, and preference for vegan diets that contain functionally active ingredients with health-promoting characteristics. Due to health, ecological, and ethical concerns, many customers are interested in reducing their usage of animal products like bovine milk. A variety of plant-based beverage substitutes are being created by the food sector as a result. To create viable alternatives, it is first necessary to provide an overview of the chemical composition, structure, features, and nutritional attributes of ordinary bovine milk. Sensory acceptability in the case of substitutes for beverages made from legumes is a significant barrier to their widespread acceptance, and thus saliva acts as a sophisticated fluid that serves a variety of purposes in the cavity of the mouth. Designing and producing next-generation plant-based beverages that mimic the physicochemical and functional qualities of conventional bovine-based beverages is gaining popularity, and many of these products can be thought of as colloidal materials that contain the particles or polymers that give them their unique qualities NG-PB foods can have a wide range of rheological qualities, such as fluids with low viscosity (such as plant-based beverages), high-viscosity liquids (like creams), soft liquids (like yogurt), as well as hard solids (such as some cheeses).

Rationalizing Euclidean Assemblies of Hard Polyhedra from Tessellations in Curved Space.

Entropic self-assembly is governed by the shape of the constituent particles, yet apriori prediction of crystal structures from particle shape alone is nontrivial for anything but the simplest of space-filling shapes. At the same time, most polyhedra are not space filling due to geometric constraints, but these constraints can be relaxed or even eliminated by sufficiently curving space. We show using MonteCarlo simulations that the majority of hard Platonic solids self-assemble entropically into space-filling crystals when constrained to the surface volume of a 3-sphere. As we gradually decrease curvature to "flatten" space and compare the local morphologies of crystals assembling in curved and flat space, we show that the Euclidean assemblies can be categorized as either remnants of tessellations in curved space (tetrahedra and dodecahedra) or nontessellation-based assemblies caused by large-scale geometric frustration (octahedra and icosahedra).

Novel ZrB2 and HfB2 metaldiboride coatings by LPCVD

The synthesis of metal diboride thin films has recently attracted great interest. Boron forms binary compounds with most metals. In general, these materials are high-melting, extremely hard solids with high degrees of thermal stability and chemical inertness.In this work the preparation of metal diboride coatings of ZrB2 and HfB2 by CVD is described. A low-pressure CVD (LPCVD) process using MeCl4 (Me = Zr or Hf), BCl3, H2 and Ar was applied. Diboride layers were prepared at deposition temperatures between 800 °C and 1000 °C. The coatings were characterized with respect to phase composition, crystal structure, hardness and wear behavior. The deposited diboride layers show well defined crystallites with a high hardness up to 3200 HV[0.01] for ZrB2 and 3900 HV[0.01] for HfB2. Depending on the substrate temperature and precursor ratio, layers with different textured crystalline structure were obtained at different deposition rates. Phase composition and structure of the deposited layers were examined using SEM and EDS-analysis.A TiN bonding layer prior the diboride deposition ensures a strong adhesion to the hard metal inserts. Scratch test measurements showed critical loads of about 90 N. In wear tests a high performance of the CVD diboride coatings were observed. HfB2 coated inserts exceeded the lifetime of state-of-the-art CVD-TiB2 coatings in face-milling TiAl6V4.

Modeling the rheological properties of plant‐based foods: Soft matter physics principles

AbstractThere is growing interest in the design and fabrication of next‐generation plant‐based (NG‐PB) foods that have physicochemical and functional properties that simulate those of traditional animal‐based foods, like meat, seafood, egg, and dairy products. Many of these products are colloidal materials containing particles or polymers, which means that their properties can be understood using soft matter physics concepts. The rheological properties of NG‐PB foods may vary widely, including low‐viscosity fluids (like milk), high‐viscosity fluids (creams), soft solids (like yogurt), and hard solids (like some cheeses). For manufacturers of NG‐PB foods to mimic this broad range of products it is important to have theoretical models to identify, predict, and control the key parameters impacting their textural attributes. In this article, the theoretical models developed to describe the properties of fluid, semi‐solid, and solid colloidal dispersions are summarized, and their potential for improving the design and fabrication of NG‐PB foods is highlighted. In the future, it will be important to establish the most appropriate models for different categories of NG‐PB foods and to determine their range of applications.

Effects of dispersion corrections on the theoretical description of bulk metals

The addition of a London dispersion correction to standard Kohn-Sham density-functional theory is essential for an accurate description of noncovalent interactions. While several dispersion-corrected density functionals (DC-DFs) have shown excellent performance for hard solids at ambient conditions, their transferability to metallic systems at ambient conditions or under isotropic compression has not been systematically examined. In this study, we assess the ability of selected DC-DFs to describe the equations of state (EOSs) of selected elemental metals and intermetallic compounds up to several gigapascals of pressure. EOS-derived properties, such as the unit-cell volume, the bulk modulus, and its pressure derivative, were then evaluated with and without thermal effects and the results compared with experimental reference data. We also assess the ability of the DC-DFs to predict the phase-transition pressures for a set of intermetallic compounds. The results of this study establish that London dispersion physics, and even dispersion contributions from the core electrons, is important in the description of bulk metals.

Numerical simulations of grinding force and surface morphology during precision grinding of leucite glass ceramics

• A force model of grinding of leucite glass ceramics is developed. • A surface morphology model of grinding of leucite glass ceramics is developed. • Elastic-to-plastic and brittle-to-ductile transitions are considered in the models. • The predicted errors of two models are within 10% and 15%. Leucite glass ceramics are high-performance denture materials due to their high mechanical strength, excellent light transmittance, and excellent biocompatibility. Glass-ceramic denture must be processed using precision grinding technology to achieve a satisfactory surface integrity. To understand the contact interaction between the abrasives and workpiece, a theoretical model of grinding force during grinding of leucite glass ceramics was developed by considering elastic-to-ductile transition depth, brittle-to-ductile transition depth, strain rate effect, and random distributions of the abrasive position and size. In addition, a surface morphology model was developed to understand the material removal and deformation behaviors during grinding of leucite glass ceramics, which considered the brittle-to-ductile transition depth, elastic recovery, and random distributions of the abrasive position and size. The mechanical properties of leucite glass ceramics used in the models were measured by nanoindentation and nanoscratch tests. Grinding experiments of leucite glass ceramics were performed to verify the accuracy of the models, and the results showed that the predicted errors of the force and surface morphology models were within 10% and 15%, respectively. Both theoretical and experimental results demonstrated that small abrasive size, low feed speed, small grinding depth, and high grinding speed were beneficial to improving the surface quality, and large abrasive size, low feed speed, small grinding depth, and high grinding speed were beneficial to decreasing the grinding force. The results will provide a theoretical guidance for optimizing process parameters during high-efficiency and precision grinding of hard and brittle solids. Graphical Abstract .

A nonlinear constitutive model for some hard electro-elastic solids. Solutions of some boundary value problems

A constitutive equation for a class of electro-elastic solid is proposed, neglecting dissipation of energy, and assuming that the gradient of the displacement field is small (the above implies the strains are small). Using the theory of implicit constitutive relations developed by Rajagopal and co-workers, a constitutive equation is proposed where the linearized strain is a function of the Cauchy stress and the electric field. The polarization field is assumed to be a function of the Cauchy stress and the electric field as well. The material parameters are adjusted to model the behaviour of some ceramic-like materials. Several boundary problems are solved to study the predictions of these new constitutive equations.

Brittle Solids: From Physics and Chemistry to Materials Applications

Hard solids with predominantly covalent–ionic bonding are finding rapidly increasing usage in many modern technologies. However, this class of solids is severely limited by their intrinsic brittleness—they break easily. It is in this context that a fundamental knowledge of brittle fracture mechanisms is of practical importance. This review covers the essential features of crack behavior in characteristically brittle solids, starting with fundamental physical and chemical models, with distinctions between equilibrium and kinetic states, stability and instability, and crack propagation and initiation. Means of imparting higher strength and toughness to otherwise brittle materials are then explored along with their pros and cons. Select technological areas where fracture properties constitute a vital facet of material function—windows and display panels, structural ceramics, biomaterials, layer structures, manufacturing, and nanomechanics—are then presented as illustrative case studies. The balance between factors such as strength and toughness, scaling and threshold effects, and crack containment and crack avoidance, as well as structure at the atomic and microstructural scales, emerge as critical factors in materials design.

Оleogels – Types, Properties and Their Food, and Other Applications

This review aims to reveal a modality for transforming liquid vegetable oils into semi-solid forms as their mechanical properties can vary from viscous and thick liquids to hard and elastic solids. The edible oleogels are an alternative replacer of undesirable trans and saturated fats. They are porous materials with self-assembled and three-dimensional gel network. Large amount of a continuous edible liquid-oil phase can be entrapped physically and stored in this gel structure. The bigels are a variety of oleogels and they represent two-phase emulsions, containing both oil-based oleogels and water-based hydrogels. The edible oleogels are composed by a structurant substance of food grade in a low concentration, below 10 %. Some of their featured properties are: (i) improved viscosity, spreadability and some of them are semisolid, translucent with semi-crystalline structure; (ii) high physical and structural stability combined with high oil binding capacity; (iii) high-temperature stability, but some of them are thermo-reversible; (iv) higher oxidative stability of oil and the chemical stability of active lipophilic compounds incorporated; (v) microbiological stability. Their more remarkable food applications are chocolates, processed meat products, margarine spreads and shortening. Their combination with other promising techniques raises up new perspectives for structural engineering of foods. There are also outlined other applications of oleogels in cosmetic and pharmaceutical formulations; for engineering purposes and environmental protection. The general limitations, some challenges in the development of new products, their commercialization are also divulged.

Photoswitchable solvent-free DNA thermotropic liquid crystals toward self-erasable shape information recording biomaterials.

Soft thermotropic liquid crystals (TLCs) have advantages on processability and shape memory compared to hard solids and fluids. The development of photoswitchable soft TLCs based on biomolecules would afford reworkable shape information recording biomaterials for the areas requiring biocompatibility and degradability. In recent years, anhydrous DNA TLCs composed of DNA and ammonium surfactants have been receiving continuous attention. However, the photoswitchable phase transition has not been realized for soft DNA TLCs at room temperature, owing to the absence of functional ammonium surfactant. Herein, a new type of azobenzene-containing surfactant would be applied to the fabrication of soft DNA TLCs with photoresponsive physical properties. The double-chain design of the used surfactant and the use of DOAB as a dopant guarantee the soft state of DNA TLCs at r.t., which also facilitates the azobenzene isomerization by reducing the packing density of surfactants. With the assistance of photoisomerization of azobenzene, the reported DNA TLCs achieve reversible liquid crystal-isotropic liquid transition at temperatures below clearing points even at room temperature. The repeatable shape information recording and self-erasing tests indicate these DNA TLCs would be good shape information recording biomaterials in the future. This work also provides a useful strategy for designing photoresponsive soft biomaterials based on rigid biomolecules like DNA.

Spatio-seasonal microplastics distribution along a shallow coastal lagoon ecocline within a marine conservation unit

The aim of our study is to estimate the abundance and sources of floating microplastics (MPs) along a coastal lagoon ecocline in a marine conservation unit (MCU) for implementing effective prevention and mitigation actions in South Brazil. MPs were sampled monthly, and the abundance and size were determined for hard solids, soft plastic, plastic filaments, and paint fragments. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis was performed, and the MPs were classified as polyethylene, polyester, polypropylene, polybutadiene, and polystyrene. Downstream areas (outside of the MCU) showed high levels of MPs, during the winter, due to low precipitation and the predominance of S/SE winds. During summer, precipitation increases, and MPs are exported with surface runoff, resulting in lower level of MPs. Outside MCU areas, a high concentration of tourism houses, commercials, and artisanal fisheries were observed, which could contribute to all types of plastic debris found in our study.

Wave propagation across a functionally graded interphase between soft and hard solids: Insight from a dynamic surface elasticity model

Joining soft to hard materials is a challenging problem in modern engineering applications. In order to alleviate stress concentrations at the interface between materials with such a mismatch in mechanical properties, the use of functionally graded interphases is becoming more widespread in the design of the new generation of engineered composite materials. However, current macroscale models that aim at mimicking the mechanical behavior of such complex systems generally fail in incorporating the impact of microstructural details across the interphase because of computational burden. In this paper we propose to replace the thin, but yet finite, functionally graded interphase by a zero-thickness interface. This is achieved by means of an original model developed in the framework of surface elasticity, which accounts for both the elastic and inertial behavior of the actual interphase. The performance of the proposed equivalent model is evaluated in the context of elastic wave propagation, by comparing the calculated reflection coefficient to that obtained using different baseline models. Numerical results show that our dynamic surface elasticity model provides an accurate approximation of the reference interphase model over a broad frequency range. We demonstrate application of this modeling approach for the characterization of the graded tissue system at the tendon-to-bone interphase, which fulfills the challenging task of integrating soft to hard tissues over a submillimeter-wide region.

Fourier and Laplace-like low-field NMR spectroscopy: The perspectives of multivariate and artificial neural networks analyses

Low field Nuclear Magnetic Resonance (LF-NMR) is a rich source of information for a wide range of samples types. These can be hard or soft solids, such as plastics or elastomers; bulk liquids or liquids absorbed in porous materials, and can come from biomaterials, biological tissues, archaeological artifacts, cultural heritage objects. LF-NMR instruments present a significant advance especially for in situ, ex situ and in vivo measurement of relaxation and diffusion. Moreover, high resolution 1D and 2D spectroscopy, as well as magnetic resonance (MR) imaging are available in these fields. In this work we discuss the advanced analysis of the data measured in LF-NMR from the perspectives of tertiary level that implies the analysis on principal components (PCA), and on the quaternary analysis that uses an artificial neural network (ANN). The principles of PCA and ANN are largely discussed. For the PCA analysis, a series of 52 spectra were analyzed, having been recorded in vivo by LF-NMR. Of these spectra, 38 were generated from normal uterus, 7 by uterus tissue with endometrial cancer, and another 7 were obtained from tissues of women with uterine cervical cancer. The PC1 vs PC2 plot was further analyzed using an artificial neural network, and the results are presented as 2D maps of probability. Furthermore, the perspectives of applying an ANN to solve the problem of Laplace-like inversion are discussed. An example of such ANN was presented and the performance was discussed. Finally, a model of complex ANN, capable to sequentially solve this kind of problems specific to LF-NMR is proposed and discussed.

INFLUENCE OF IMPERFECT THERMAL CONTACT ON HEAT EXCHANGE IN THE SYSTEM OF MULTILAYER CYLINDRICAL BODIES

Introduction. Solving the problem of heat transfer in multilayer structures devoted a large number of works. The vast majority of them are limited to the case of perfect thermal contact between the layers. However, according to the authors, the problems of thermal conductivity in multilayer structures using into account the imperfect thermal contact are insufficiently studied. The number of such studies is quite limited. Also, known studies are usually limited to two layers. That is because the increase in the number of layers (given the choice of methods of practical implementation) leads to several computational difficulties. Therefore, the problem of constructing an effective analytical scheme for the study of heat transfer processes in multilayer structures in the presence of imperfect thermal contact between the layers remains an urgent task.Purpose. Application of the direct method to the study of heat transfer processes in the system "continuous cylinder inside a multilayer cylindrical shell" with imperfect thermal contact.Methods. An auxiliary problem set for the distribution of the temperature field in a multilayer solid cylindrical hollow body (a cylinder of the sufficiently small radius is "removed") taking into account the imperfect thermal contact between the individual layers. According to the already known scheme of the direct method solve this problem.Results. Boundary transition obtained the solution of the original problem. Boundary transition: the radius of the"removed" cylinder, with the centre at the origin, goes to zero. This approach established that the solution to the problemis limited in the whole structure. In this case, the solution obtained explicit formulas.Conclusions. Effective analytical scheme constructed for application of the direct method to the study of heattransfer processes in multilayer hard cylindrical solids taking into account the non-ideal thermal contact between thelayers. The number of layers, their size and arrangement are considered arbitrary.

Tribological Analysis of Contacts Between Glass and Tungsten Carbide Near the Glass Transition Temperature

In recent years, the tribological contact between hard solids and glass at high temperatures has been identified as a crucial aspect in emerging technical applications like e.g., precision glass molding. To optimize such tribological systems, especially, the internal transformations of the glasses need to be considered, since these can determine which kind of energy dissipation channels become relevant, when the temperature of a glass is increasing and approaching the glass transition temperature. Here, we now introduce a new tribometer specifically developed for the analysis of glasses at elevated temperatures. Using this tribometer, we characterize friction of contacts between tungsten carbide (WC) and soda lime glass as a function of temperature, while additionally PMMA was analyzed for comparison. Our experiments reveal different tribological regimes where either simple sliding, surface fracturing, or surface deformation can be identified as relevant interface processes for the tribological behavior.Graphical

Application of XDM to ionic solids: The importance of dispersion for bulk moduli and crystal geometries.

Dispersion corrections are essential in the description of intermolecular interactions; however, dispersion-corrected functionals must also be transferrable to hard solids. The exchange-hole dipole moment (XDM) model has demonstrated excellent performance for non-covalent interactions. In this article, we examine its ability to describe the relative stability, geometry, and compressibility of simple ionic solids. For the specific cases of the cesium halides, XDM-corrected functionals correctly predict the energy ranking of the B1 and B2 forms, and a dispersion contribution is required to obtain this result. Furthermore, for the lattice constants of the 20 alkali halides, the performance of XDM-corrected functionals is excellent, provided that the base functional's exchange enhancement factor properly captures non-bonded repulsion. The mean absolute errors in lattice constants obtained with B86bPBE-XDM and B86bPBE-25X-XDM are 0.060 Å and 0.039 Å, respectively, suggesting that delocalization error also plays a minor role in these systems. Finally, we considered the calculation of bulk moduli for alkali halides and alkaline-earth oxides. Previous claims in the literature that simple generalized gradient approximations, such as PBE, can reliably predict experimental bulk moduli have benefited from large error cancellations between neglecting both dispersion and vibrational effects. If vibrational effects are taken into account, dispersion-corrected functionals are quite accurate (4 GPa-5 GPa average error), again, if non-bonded repulsion is correctly represented. Careful comparisons of the calculated bulk moduli with experimental data are needed to avoid systematic biases and misleading conclusions.

Dynamic Viscosity and Transverse Ultrasonic Attenuation of Engineering Materials

In this paper, ultrasonic attenuation of the transverse waves of engineering materials is evaluated, covering metals, ceramics, polymers, fiber-reinforced plastics, and rocks. After verifying experimental methods, 273 measurements are conducted and their results are tabulated. Fifty of the tests are for the longitudinal mode. Attenuation behavior is determined over broadband spectra. The attenuation spectra are characterized in four patterns, with 2/3 of the tests showing linear frequency dependence and another ¼ linear spectrum plus Rayleigh scattering (Mason-McSkimin relation). The longitudinal and transverse damping factors varied from 0.004 to 0.065, which are 1/3 to 5 times those of polymethyl methacrylate, suggesting that almost all the engineering materials tested may be viscoelastic. The present test results make the term dynamic viscosity more appropriate for exploring the underlying processes. The observed results were compared between the longitudinal and transverse modes and among similar material types. In more than a half of the tests, the transverse attenuation coefficients were higher than the corresponding longitudinal attenuation coefficients by 1.5× or more. Some material groups had similar attenuation coefficients for the two modes. Since the physical basis for viscous damping is hardly understood, especially in hard solids, further studies from new angles are keenly desired. This collection of new attenuation data will be of value for such works. Practically, this will assist in materials selection and in designing structural health monitoring and non-destructive inspection protocols.

The Effect of Addition of Powder Areca Nut Midrib on Polyester Matrix to the Tensile and Bending Strength

In this life, humans certainly need a variety of equipment called material. In its development the material continues to experience progress as in early life, humans only use equipment made from simple materials such as wood, stone and others. Then move to the metal and the last to use a lot of mixture in the refinement of these materials, one form of mixed material created by humans is composite. Betel nut has a lot of powder, how to take it without damaging the areca nut plant. After the extraction of powder is applied to the areca nut, the fiber will be mixed with polyester resin as its matrix. Polyester resin is a matrix of composites. This resin is also included in thermoset resin. In the thermoset polyester the liquid resin is converted into hard and brittle solids formed by chemical cross-bonds that form very strong polymer chains. The mixture will produce composite materials which have different mechanical properties and characteristics from the forming material. Composite materials have the properties of conventional materials from the manufacturing process through inhomogeneous mixing. The purpose of this study was to determine the effect of adding areca nut powder to the polyester matrix on tensile and bending strength. Research and testing are carried out in several stages, including the manufacture of specimens. Both materials are stirred manually until both materials are fused evenly, then tensile and bending tests are carried out, data analysis and conclusions. The results of this research got the best tensile test values on composite polyester resin specimens and areca nut powder with a composition of 90%: 10% with a value of 5.09 MPa. And the results of bending which got the best bending test values are polyester resin composites and nutmeg powder with a composition of 90%: 10% with bending test values of 3.77MPa.

Plastic floating debris along a summer-winter estuarine environmental gradient in a coastal lagoon: how does plastic debris arrive in a conservation unit?

Improper management of plastic waste is an important contributor to the pollution in water bodies. However, how floating plastic debris is transported to coastal lagoons and marine conservation units is still poorly understood. This work determined the level of contamination due to floating plastic debris in Acaraí Lagoon by establishing density distribution patterns along the lagoon ecocline in the winter and summer. Four areas were chosen that followed the estuarine gradient of the lagoon (external, lower, middle, and upper), and in each area, three samples of were collected by trawling with a plankton net. The plastic debris was classified into paint fragments, hard solids, plastic filaments, and soft plastics, and the plastic debris density and surface area were determined in each sampling area. The concentrations of the plastics in the downstream and upstream areas resulted from the high density of debris that occurred during the winter due to the absence of rain and the entry of coastal waters into the lagoon. The reduced abundance and surface area of the plastics in the summer were related to the substantial output of water from the interior of the lagoon to the mouth of the lagoon due to high rainfall during this season. The absence of plastic waste management actions and developed areas at the mouth of the lagoon that were associated with the spatial and temporal fluctuations in the environmental variables favored the occurrence and high abundance of plastic debris in the water column, contaminating the entire system of Acaraí State Park.