Formation Of New Surfaces Research Articles

Microstructure study of natural marine clay in loading and unloading processes

The microstructure evolutions of natural marine clay during loading and unloading processes were investigated using undrained triaxial tests. The pore distribution and arrangement of soil particles and aggregates were measured by mercury intrusion porosimetry (MIP) and field emission scanning electron microscope (FESEM) tests, respectively. The results show that pores do not always collapse into smaller ones with stress levels increasing; the destruction of cemented soil structure will lead to the connection of small pores into large pores. In the consolidation process, as the consolidation pressure increased from 0 to 100 kPa, the total specific surface decreased from 20.01 mm2/g to 17.42 mm2/g. Conversely, the total specific surface increased from 17.42 mm2/g to 19.25 mm2/g as the confining pressure surpassed the preconsolidation pressure, indicating the formation of new surfaces. The rebound effect during the unloading process is another factor causing the increase in pore volume, but the destruction of the soil structure can significantly reduce this effect. The microscopic morphology at the point of soil failure under high stress levels in both loading and unloading processes tended to be similar, as the soil structure was completely destroyed.

Investigation of the influence of technological factors and compositions of binders on the strength characteristics of blast–furnace cement with magnetized ferromagnetic additives

Cement production is a significant source of carbon dioxide emissions. One of the ways to reduce emissions is to reduce the proportion of clinker in cement by introducing active mineral additives into its composition, particularly granulated blast-furnace slag. One of the ways to increase the activity of such cement is the effect of magnetic fields on the spin multiplicity of the substances involved in the hardening reaction. In this case, the maximum effect is ensured by introducing a magnetized finely dispersed ferromagnetic substance into the cement composition. The activation effect depends on the additive’s adding method to the cement’s composition, the components ratio in the cement, and the cement hardening mode. This work aims to identify the influence of the adding method of the additive, the slag and additive proportion in cement, and the steam curing temperature on the activity effect of the binder. Three groups of studies were carried out to determine the strength characteristics of laboratory samples hardened both in natural conditions and during steaming. In the first group, cement samples have tested containing 40% slag obtained by joint grinding and joint mixing of the additive with cement for 0.5, 1, 2, 4 and 8 minutes. In the second group, samples have tested with the additive amount varied from 0 to 2.5%, and slag amount from 0 to 80%. Finally, cement samples were tested in the third group containing 50% slag and from 0 to 2.5% additive. The samples were steam cured at temperatures ranging from 50 to 90° C and tested one day, 28 and 90 days after steam curing. As a result of the research, it has revealed that to obtain the maximum effect, the additive must be introduced into the cement composition by joint grinding. The factors influencing the activity have been determined. At the same time, the time of joint grinding should ensure uniform mixing of the components and the formation of new surfaces of cement grains in the presence of magnetic fields. Too long joint grinding leads to the loss of the magnetic properties of the addition. It was found that the activation effect from the additive addition increases with an increase in the proportion of slag. In cement without slag, an increase in the additive content leads to a drop in strength. It was revealed that the introduction of magnetized ferromagnetic dust additives into the composition of the SPC makes it possible to reduce the steam curing temperature of products by 20-25° C. Studies have shown that using a finely dispersed ferromagnetic substance as an activating additive can save energy resources and reduce emissions.

Research on electromagnetic wave absorption properties of zinc-based acrylate resins for marine antifouling coating

Here, we report on the marine antifouling performance and electromagnetic wave absorption (EMWA) properties of multifunctional zinc-based acrylate resins (ARZn-x). Their controlled hydrolysis with varying contents of carboxylic acid groups and ZnO led to formation of new surfaces that contributed to excellent antibacterial activity (>90%) and reductions in algal adhesion (optimal: 92.5%). Marine field tests demonstrated ideal antifouling performance during immersion in seawater for 4 months, and the coatings inhibited the adhesion and growth of biofouling species in marine. Furthermore, the ARZn-x resin coatings exhibited remarkable EMWA performance, with an RLmin of − 40.18 dB at 1.5 mm and 30.55 GHz, and full absorption of frequencies ranging from 18 to 40 GHz was achieved with thicknesses ranging from 1.0 to 5.5 mm. These resins provide new approaches to the development of multifunctional materials demonstrating marine antifouling performance and EMWA properties.

Use of Digital Twins for Mathematical Modeling of Ultrasonic Cutting of Titanium Blanks

The paper presents the results of numerical experimental studies of cutting titanium blanks using mathematical modeling programs, which make it possible to completely repeat technological processes in a computer (digital twin). The LS-DYNA product was used as a program to simulate the process of stock removal from titanium blank. It has been established that the use of this method adequately describes the cutting processes, including with the introduction of the energy of an ultrasonic field into the processing zone, can significantly reduce the duration of experimental research and evaluate the influence of the elements of the cutting mode and design parameters of the tool on the thermal power aspects of the formation of new surfaces of machine parts.

Stress-Dependent Particle Interactions of Magnesium Aluminometasilicates as Their Performance Factor in Powder Flow and Compaction Applications.

In the pharmaceutical industry, silicates are commonly used excipients with different application possibilities. They are especially utilized as glidants in low concentrations, but they can be used in high concentrations as porous carriers and coating materials in oral solid drug delivery systems. The desirable formulations of such systems must exhibit good powder flow but also good compactibility, which brings opposing requirements on inter-particle interactions. Since magnesium aluminometasilicates (MAS) are known for their interesting flow behavior reported as “negative cohesivity” yet they can be used as binders for tablet compression, the objective of this experimental study was to investigate their particle interactions within a broad range of mechanical stress from several kPa to hundreds of MPa. Magnesium aluminometasilicate (Neusilin® US2 and Neusilin® S2)-microcrystalline cellulose (Avicel® PH102) physical powder mixtures with varying silicate concentrations were prepared and examined during their exposure to different pressures using powder rheology and compaction analysis. The results revealed that MAS particles retain their repulsive character and small contact surface area under normal conditions. If threshold pressure is applied, the destruction of MAS particles and formation of new surfaces leading to particle interactions are observed. The ability of MAS particles to form interactions intensifies with increasing pressure and their amount in a mixture. This “function switching” makes MAS suitable for use as multifunctional excipients since they can act as a glidant or a binder depending on the applied pressure.

Injection lap riveting

This paper presents an injection lap riveting process to connect two sheets placed one on top of the other. The process is carried out at ambient temperature and differs from self-pierce riveting because its joining principle is based on plasticity and friction without fracture and formation of new surfaces. The working principle is based on two consecutive operations - first, a dovetail ring hole is machined in the lower sheet and then a semi tubular rivet is injected through the upper sheet into the dovetail ring hole of the lower sheet, by compression with a punch. The presentation is based on a combined experimental and numerical investigation and special emphasis is put on the influence of the dovetail ring hole geometry in material flow, riveting force, and pull-out and shear destructive forces. The last past of the paper includes details of a prototype cutting tool that was developed by the authors for producing the dovetail ring holes in-site and fostering the portability and applicability of the process.

Modeling snow slab avalanches caused by weak-layer failure – Part 2: Coupled mixed-mode criterion for skier-triggered anticracks

Abstract. Using the analytical model presented in Part 1 of this two-part paper, a new conceptual understanding of anticrack nucleation in weak layers is proposed. To obtain a sufficient condition for onset of failure, two necessary conditions must be satisfied simultaneously: (i) the weak layer must be overloaded in terms of stress and (ii) the initiating crack must release enough energy for the formation of new surfaces. This so-called coupled criterion was proposed by Leguillon (2002). No assumptions on initial defects within the weak layer are needed. Instead, the failure criterion provides both critical loading and the size of initiating cracks. It only requires the fundamental material properties strength and fracture toughness as inputs. Crack initiation and subsequent propagation are covered by a single criterion containing both a strength-of-materials and a fracture mechanics condition. Analyses of skier-loaded snowpacks show the impact of slab thickness and slope angle on critical loading and crack initiation length. In the limit cases of very thick slabs and very steep slopes, we obtain natural avalanche release. A discussion of different mixed-mode stress and energy criteria reveals that a wrong choice of mixed-mode hypotheses can yield unphysical results. The effect of material parameters such as density and compliance on weak-layer collapse is illustrated. The framework presented in this two-part series harnesses the efficiency of closed-form solutions to provide fast and physically sound predictions of critical snowpack loads using a new conceptual understanding of mixed-mode weak-layer failure. It emphasized the importance of both stress and energy in avalanche release.

Effect of normal scratch load and HF etching on the mechanical behavior of annealed and chemically strengthened aluminosilicate glass

Micro-cracks generated by hard body scratch are a major cause of strength decrease for silicate glass. The influence of normal scratch load on the cracking patterns and flexural strength of annealed glass (AG) and chemically strengthened glass (CSG) were studied. With the increase of the normal load, the load capacity of scratched AG specimens decreased to about 40 MPa at 20gf immediately. However, the residual strength of CSG decreased to a steady value of 145 MPa as the scratch load increased to 500gf. Then the effect of hydrofluoric acid (HF) etching on the surface morphology and mechanical properties of the 500gf scratched glass were investigated. After 8min (for CSG) and 16 min (for AG) acid treatment, the flexural strength of CSG and AG increased to a considerable value of 900 MPa, which is 3.6 and 5.5 times higher than the flexural strength of undamaged specimens. Microscopic observations show that the blunting and eliminating of median cracks as well as the formation of new surfaces are the main causes of strength enhancement.

Simple Interpretation of Kinetics of Fast Solid-State Reactions

A simple model of fast solid-state reaction of two substances on the phase boundary is proposed. It is assumed that the reaction is controlled by the formation of new surface. The dependence of a change in the surface on the value of shear deformation is calculated. Thus, the relation between the product yield and shear deformation independently of time is explained.

Modeling and Investigation of the Stability of a Multicutter Turning Process by a Trace

The results of modeling and investigation of the stability of a continuous multicutter turning process are presented. The mathematical modeling is based on an equation for the formation of new surfaces, on equations of motion, and on the fractional-rational cutting law. The influence of the parameters of the technological system on the stability of the continuous cutting mode is analyzed.

Nanoencapsulation of hexavalent chromium with nanoscale zero-valent iron: High resolution chemical mapping of the passivation layer

Solid phase reactions of Cr(VI) with Fe(0) were investigated with spherical-aberration-corrected scanning transmission electron microscopy (Cs-STEM) integrated with X-ray energy-dispersive spectroscopy (XEDS). Near-atomic resolution elemental mappings of Cr(VI)–Fe(0) reactions were acquired. Experimental results show that rate and extent of Cr(VI) encapsulation are strongly dependent on the initial concentration of Cr(VI) in solution. Low Cr loading in nZVI (<1.0wt%) promotes the electrochemical oxidation and continuous corrosion of nZVI while high Cr loading (>1.0wt%) can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr(VI) (e.g., <10mg/L). Whereas the reacted nZVI is quickly coated with a newly-formed layer of 2–4nm in the presence of concentrated Cr(VI) (e.g., >100mg/L). The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy (XPS) depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe(III)–Cr(III) (oxy)hydroxides with Cr(VI) adsorbed on the outside surface. The insoluble and insulating Fe(III)–Cr(III) (oxy)hydroxide layer can completely cover the nZVI surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZVI in high Cr(VI) solution is detrimental to the performance of nZVI for Cr(VI) treatment and remediation.

Luminescence from impact- and abrasive-damaged ZnS ceramics

IR windows made of ZnS ceramics serve as protective elements for the thermal imaging systems established on mobile carriers, whereon they suffer from weathering and dust impacts. In this study, the erosion of ZnS ceramics was simulated by the abrasive damaging of polished specimens, and the response of the crystal lattice on the external forcing was investigated by the method of photoluminescence (PL). Impacts of isolated hard particles were modelled with the discrete shocks of a pointed striker, and fractoluminescence (FL) from the damaged spot was detected. The FL evidenced that the impact forcing triggers a two-stage mechanism of damage nucleation in this ductile ceramic. The dislocation motion at the stage of initial deformation followed by the interatomic bonds breakage at the stage of cracking. The PL data showed the higher stability of crystallites in chemically vapor-deposited (CVD) ZnS ceramics as compared with the same compounds obtained by the hot pressing (HP) or physical vapor-deposition (PVD) technologies. The abrasive treatment of ZnS-CVD did not affect significantly the entirety of crystallites because of plasticity of intercrystallite substance, in which the impact-induced tension dissipated. Undamaged crystallites retained their optical properties that is did not exhibit additional absorbance. Thus, the decrease of the transmissive capability under particle impacts occurs predominantly due to light scattering on the newly-formed surface irregularities.

Pullout behavior of large-diameter collapsed double-walled carbon nanotubes

The pullout behavior of large-diameter collapsed double-walled carbon nanotubes (DWCNT) was studied by molecular dynamics simulations and compared with those in the circular cross-sectioned state. The pullout force-displacement curves of both are in good agreement with the same mean value of the pullout force during the steady pullout stage. The pullout force was mainly due to the formation of new surfaces; the friction between nested walls was negligible. The effects of different chiral combinations and inter-wall spacings on the pullout behavior for both section situations were investigated. The commensurate (zigzag/zigzag or armchair/ armchair) bi-tube systems have a larger fluctuation in the pullout force. The smaller interspacing implies lower mean pullout force with stronger fluctuations.

Influence of weathering on the leaching behaviour of zinc and PAH from synthetic sports surfaces

Synthetic materials used for outdoor sports grounds consist of a mix of inorganic, organic and polymeric compounds that show ageing due to weathering and a complex leaching behaviour by percolation of rainwater, which can limit its lifetime. Additionally, weathering exposure induces degradation processes in the polymers, which leads to the formation of new surfaces allowing water to access additional reservoirs of leachable compounds. A laboratory test comprising artificial weathering, ozonisation and subsequent leaching was developed to investigate this behaviour in a reproducible and controllable way. The experiments showed a general decline of Zn, polycyclic aromatic hydrocarbons (PAH) and total organic carbon (TOC) concentrations after an initial increase. Within this general trend, the course of concentration over exposure duration is very specific for individual sample materials and the analyte under investigation. The results indicate that weathering and degradation behaviour cannot be predicted from initial material conditions. Thus, weathering experiments are recommended to fill this gap of knowledge.

Contribution of specific work of fracture to size effect in microcutting

ABSTRACTSpecific work of fracture (R) has been widely used to quantify the energy consumed in formation of new surfaces during metal cutting. R becomes a significant portion of total cutting energy in microcutting, thereby influencing the phenomenon of “size effect. ” Therefore, this work presents an evaluation of specific work of fracture for sharp and rounded-edged tools, knowing cutting forces and shear angles from LS-DYNA simulations of orthogonal microcutting of low-carbon AISI 1215 steel. The R was also evaluated as a function of process parameters such as cutting speed, rake angle, tool edge radius, and uncut chip thickness, so as to illustrate the effect of these variables on the magnitude of R and contribution of R to the specific cutting energy or “size effect.” It is observed that R increases with an increase in uncut chip thickness, whereas it decreases with an increase in cutting speed, rake angle, and tool edge radius. UR defines the contribution of fracture to the specific cutting energy (U) due to specific work of fracture R. At all the parametric conditions, the contribution of fracture is higher at lower uncut chip thickness and it is of 8–36% in microcutting of AISI 1215 steel.

Different growth mechanisms of Ge by Stranski-Krastanow on Si (111) and (001) surfaces: An STM study

Structural and morphological features of the wetting layer formation and the transition to the three-dimensional Ge growth on (111) and (100) Si surfaces under quasi-equilibrium growth conditions were studied by means of scanning tunneling microscopy. The mechanism of the transition from the wetting layer to the three-dimensional Ge growth on Si was demonstrated. The principal differences and general trends of the atomic processes involved in the wetting layers formation on substrates with different orientations were demonstrated. The Ge growth is accompanied by the Ge atom redistribution and partial strain relaxation due to the formation of new surfaces, vacancies and surface structures of a decreased density. The analysis of three-dimensional Ge islands sites nucleation of after the wetting layer formation was carried out on the (111) surface. The transition to the three-dimensional growth at the Si(100) surface begins with single {105} facets nucleation on the rough Ge(100) surface.

Polymer Foams Made of Immiscible Polymer Blends Compatibilized by Janus Particles—Effect of Compatibilization on Foam Morphology

Polymer blends have the potential to be homogenously foamed, since the interface area between their phases can be used as bubble nucleating agents during the foaming process. Immiscible polymer blends of poly(2,6‐dimethyl‐1,4‐phenylene ether) PPE and poly(styrene‐co‐acrylonitrile) SAN with a weight ratio of 60/40 are compatibilized by different amounts (1–10 wt%) of Janus nanoparticles (JPs). Here, we report on the nucleation effect of JPs and the dispersed PPE phase on the foaming behavior of PPE/SAN blends. The plasticization of CO2 and its solubility and diffusion behavior in the PPE/SAN blend are analyzed and correlated to blend morphologies. It is shown that partial coverage of the raspberry structure results in stress concentration at the blend interface during the saturation step. This formation of new surfaces by cleavage (and maybe microcrazes) results in a higher sorption of the blowing agent, which affects the foaming behavior. Through temperature‐induced batch foaming with CO2, the blends are foamed to find the optimum foaming conditions and relationships between the morphology of the compact and foamed blends (cellular structure) and the density are established. Finally, it was concluded that by using Janus particles, homogenous foams with small cell sizes, and relatively high densities are produced.

Effect of Substrate Surface Oxide Film Thickness on Deposition Behavior and Deposition Efficiency in the Cold Spray Process

The mechanism of cold spray deposition is not yet completely understood. The impinging velocity and deformation behavior of the particles are believed to be critical deposition conditions. However, such substrate conditions as oxide-film thickness and mechanical properties may also affect cold spray deposition. In this study we investigated the effect of substrate conditions, especially oxide film thickness, on the deposition process. The efficiency of deposition and the relationship between the impinging position of the particles and the number of particles deposited were investigated for two substrates coated with oxide films of different thickness; the particles were deposited sparsely on the substrates. Results showed that efficiency of deposition was lower for the oxide film with the greater thickness. Deposition tendency was also associated with impinging velocity, i.e., the critical velocity on which oxide film thickness depends; this is the reason for the different efficiency of deposition. An oxide film may inhibit deposition on a new surface. These results indicate that oxide film thickness has a substantial effect on the efficiency of deposition on the substrate. They also imply that creation of a newly-formed surface is important to the deposition process.

Characterisation and Mechanoluminescence studies of Sr2MgSi2O7: Eu2+, Dy3+

Di strontium magnesium silicate phosphor doped with specific concentration of Eu2+ (0.5 mol%) and Dy3+ (1.5 mol%) is prepared using solid state reaction technique. Sample was characterized by X-ray diffraction (XRD) and Fourier transforms infrared techniques. Scanning Electron Microscopy was done to see the morphology of prepared sample. Refined lattice parameters and bond lengths were calculated using the refined data. Mechanoluminescence (ML) studies were also done. Sample exhibited fairly good ML properties. ML spectra expressed single peak supports the formation of single emission centre due to transition of Eu2+ ions due to transitions from any of the sublevels of 4f65 d1 configuration to 8S7/2 level of the 4f7 configuration. Semi-log plots of ML were used to calculate ML decay constant. Calculated ML decay constant indicated that it has slow decay which is one of the properties of long lasting phosphors. It was considered that formation of new surface comprising of local and bulk piezoelectricity are responsible for ML emission. This fracto-mechanoluminescent material can be used in the devices like fracture sensor, impact sensor, damage sensors, safety management monitoring system, fuse system for army warheads, etc.

Influence of Substrate Temperature on Adhesion Strength of Cold-Sprayed Coatings

Cold spraying is a promising process for fabricating functional coatings. Because of solid state particle deposition, the electrical and chemical properties of cold-sprayed coatings are almost similar to the bulk materials. The most important factor in depositing a particle through cold spraying is known as the critical velocity. When the particle velocity is beyond the critical velocity, the plastic deformation of both the sprayed metallic particle and the metallic substrate causes the removal of surface oxide layers and newly-formed surfaces are exposed. The newly-formed surface yields the metallic bond, and then cold spray deposition can occur. Therefore, the substrate conditions must also be considered in order to understand the cold spray process. In this study, the influence of substrate temperature on the adhesion strength of coatings was investigated by substrate pre-heating. The adhesion strength was examined by a shear adhesion test. This showed that substrate pre-heating enhances the adhesion strength with a specific combination of coating and substrate materials. Thermal stress and substrate surface oxidation have been suggested ss the causes of these.