Rough Layer Research Articles

Direct additive manufacturing of transparent fused silica glasses using an integrated paste printing and laser in-situ melting technology

Fused silica glasses are of great importance for applications in optics, photonics, electronics, and biochemistry. However, their harsh processing nature still constrains the design and development of fused silica glasses for advanced applications. Additive manufacturing (AM) is among the promising techniques to improve the fabrication of fused silica glasses. Herein, we develop an integrated paste printing and laser in-situ melting technology to additively manufacture fused silica glasses without post-heat-treatments. For every layer, the fused silica paste was first printed by an air-pumped dispenser based on the predesignated CAD model, and subsequently melted by a CO2 laser to become transparent glasses. To improve the paste printing process, the shear thinning property of the developed fused silica paste was investigated to evaluate the printability of the paste, and the control strategy of the paste printing parameters was developed for precise thickness control of the printed paste layer. By optimizing the laser processing parameters, the surface waviness and roughness of the laser-melted glass layers were effectively minimized, indicating the surface uniformity was improved. To evaluate the optical properties of the laser-melted glasses, the optical transmittance and refractive indices of the fused silica glasses melted by different laser powers were characterized. Through stacking the laser-melted fused silica glasses layer-by-layer, three-dimensional (3D) fused silica glass components with unusual thin-wall structures and embedded microfluidic channels have been directly printed, demonstrating that the developed glass AM technology is promising for advanced applications such as microfluidics, integrated optics, and metamaterials.

A T-matrix approach to wave propagation and scattering in layered environments with rough interfaces

Wave propagation and interactions at the interfaces of multi-layered media can be described in terms of transition matrix coefficients, or T- matrixes, taken from solutions for a plane wave transformation, reflection, scattering, and transmission, at an interface between two homogeneous half- spaces. These solutions can be found separately for each interface of the layered system and each combination of adjacent media. Then scattering amplitudes or the T-matrix of the whole multi-layered system can be obtained using an iterative procedure that starts from a simple case of two half-spaces at the basement of the system. A quite similar iterative procedure is frequently used for calculating the reflection coefficient of compressional plane waves for a multi-layered fluid system with flat interfaces using the reflection coefficients of each interface. In this paper, we show that a similar, but a more general T-matrix approach, can be developed to include interface roughness, different types of media and waves, for instance fluid, elastic or poroelastic layers, compressional and shear waves (vertically and horizontally polarized). As an example, scattering from a rough elastic layer is considered. An explicit first-order expression for the scattering strength is obtained and it’s applications to remote sensing of sea ice layer are discussed. [Work supported by ONR.]

Tailoring optical response in nanostructured bilayers: Effects of surface roughness and layer thickness on NbN/Nb and TiN/Ti

Numerical calculations were performed on NbN/Nb and TiN/Ti nanostructured bilayers. Discrete dipole approximationimplemented in the DDSCAT code was utilized. In order to design a TUC (Target Unit Cell) with realistic surfaceroughnesspattern, Atomic Force Microscope images of 100 ±10 nm Nb thin films were used. The optical properties of nanostructured bilayers (60-100 nm thickness with a ±10 nm surface roughness) were calculated, keeping the interfacebetween the layers as smooth flat surfaces. For the NbN/Nb nanostructure with a thickness between 100 ±10 nm, and 70 ±10 nm, in a wavelength range between 200 and 350 nm, the reflectance and absorptance show a nearly flat spectrumwith an intensity of 20% and 80%, respectively. For larger wavelengths, absorptance decays smoothly. In contrast, for the 60 ±10 nm bilayer, the absorptance decays faster. For the TiN/Ti nanostructure, at 415 nm, a relative maximum in the reflectance, and a minimum in absorptance, are observed. The critical value of the absorbed light spectra begins to shift to higher wavelengths as the thickness of the TiN layer increases. We demonstrate that adding a rough nitride layer on top of its metallized layer drastically modifies the optical response of the nanostructured bilayer, an interesting result forplasmonics and nanoelectronics applications.

Catalytic thermoelectric hydrogen sensor with CoSb3 thermopile by single-step deposition on bare/textured glass

Hydrogen sensors are required due to the flammability of hydrogen in air. Catalytic thermoelectric hydrogen sensors show promise because they provide direct voltage output from a temperature difference generated by the catalytic combustion of hydrogen. CoSb3 is a good thermoelectric material for energy harvesting and sensing. However, conventional CoSb3 thermopiles require the separate deposition of p- and n-type thermoelectric elements. This study proposes the surface roughness modification of a soda-lime glass substrate through the development of a textured glass surface to prepare a CoSb3 thermopile by single-step deposition. A Co-In-Sb stack with a SiO2 capping layer is deposited by an e-beam evaporator on bare/textured glass and thermally activated under room conditions, which produces a thermoelectric pair due to the partial release of volatile Sb from cracks developed in the rough layer formed on textured glass. A thermoelectric pair consists of a CoSb3 layer with a deficiency of Sb (n-type) on textured glass and that with an excess of Sb (p-type) on bare glass. A hydrogen sensor is made with CoSb3 thermopile with 41 thermoelectric pairs and a catalyst reservoir coated with hydrogen oxidation catalyst. The sensor shows a sensitivity of 13 mV for 1 % H2 in air at room temperature.

Insights into modeling approaches for boundary- and mixed-lubricated conditions

PurposeTribological research is complex and multidisciplinary, with many parameters to consider. As traditional experimentation is time-consuming and expensive due to the complexity of tribological systems, researchers tend to use quantitative and qualitative analysis to monitor critical parameters and material characterization to explain observed dependencies. In this regard, numerical modeling and simulation offers a cost-effective alternative to physical experimentation but must be validated with limited testing. This paper aims to highlight advances in numerical modeling as they relate to the field of tribology.Design/methodology/approachThis study performed an in-depth literature review for the field of modeling and simulation as it relates to tribology. The authors initially looked at the application of foundational studies (e.g. Stribeck) to understand the gaps in the current knowledge set. The authors then evaluated a number of modern developments related to contact mechanics, surface roughness, tribofilm formation and fluid-film layers. In particular, it looked at key fields driving tribology models including nanoparticle research and prosthetics. The study then sought out to understand the future trends in this research field.FindingsThe field of tribology, numerical modeling has shown to be a powerful tool, which is both time- and cost-effective when compared to standard bench testing. The characterization of tribological systems of interest fundamentally stems from the lubrication regimes designated in the Stribeck curve. The prediction of tribofilm formation, film thickness variation, fluid properties, asperity contact and surface deformation as well as the continuously changing interactions between such parameters is an essential challenge for proper modeling.Originality/valueThis paper highlights the major numerical modeling achievements in various disciplines and discusses their efficacy, assumptions and limitations in tribology research.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2023-0076/

Heat transfer enhancement with additively manufactured rough surfaces: Insights from large-eddy simulations

To study the impact of additively manufactured (AM) roughness on fluid flow and heat transfer, we performed a series of high-fidelity large-eddy simulations on turbulent heat transfer over a three-dimensional AM rough surface with varying bulk Reynolds number and average roughness height values. We considered rough surfaces created using AM techniques at Siemens based on Nickel Alloy IN939 material with four different mean roughness heights, ks= 1.594, 1.992, 2.630, and 3.984 mm, and the simulations were performed at five bulk Reynolds numbers of 1000, 3000, 6000, 11 700, and 18 000. The temperature was treated as a passive scalar with a Prandtl number of 0.71. To better understand the effect of wall roughness on the momentum and heat transfer mechanism, mean temperature and velocity profiles as well as heat fluxes are presented. The wall-normal Reynolds stress, ⟨ux′ur′⟩, and heat flux, ⟨ur′Θ′⟩, decrease for larger wall roughness heights, Ra, and their respective magnitudes remain very similar for different Ra. A similarity rule for friction factor and heat transfer is used to correlate and interpret the numerical results and compare them with previously existing results, both theoretical and experimental. The assessment of the thermal performance factor illuminates the improvement in heat transfer with the existing surface roughness. By studying the probability density functions of the instantaneous Stanton number, the recirculation zones, which are the result of an adverse pressure gradient, were found to have a profound effect on heat transfer. This is important as it leads to the wall-scaled mean temperature profiles being of larger magnitude than the mean velocity profiles both inside and outside the roughness layer. This means that the temperature wall roughness function, ΔΘ+, differs from the momentum wall roughness function, ΔU+.

Fabrication of novel (Cr) based (MIL-101) incorporated mixed matrix forward osmosis membranes for environmental remediation

This paper focusses on the fabrication of a thin film nanocomposite forward osmosis (FO) membrane using PA support. This was done through interfacial polymerization with MOF MIL-101(Cr). There are various methods which are used for the purification of water such as ion-exchange method; reverse osmosis, adsorption, solvent extraction but these are expensive, old and timing consuming. So there is need of a unique and reliable method which is cheap, easy, less time consuming, pollution free and can give better results. For this purpose, I have worked on FO membranes with the incorporation of novel MOF MIL-101(Cr). By using different characterization methods, the surface properties, chemical composition and structure of FO membranes based on MOF MIL-101(Cr) were studied. This coating has done by layer by method therefore has larger pores to higher selective layer roughness. It also enhanced the membrane permeability and heavy metal rejection because MOF MIL-101(Cr) has unique structures and desirable mechanical and chemical properties. This MOF has high thermal stability, greater surface area and high porosity. It was observed that TNF membranes provide ultrafast nano-channels for water transport, higher water flux and lower the solute reverse flux as compared to TFC membranes without MIL-101(Cr). The results of FO thin film nanocomposite membranes based on MOF MIL-101(Cr) have shown the 81 % heavy metal rejection than simple polyamide membranes. This FO method will offer further promising applications, opportunities and excellent separation performances to produce composite membranes with thin films on microfiltration substrates to mitigate concentration polarization.

Water recovery from the high salinity brine: Effect of the interlayer structure in the polyamide nanofiltration membrane

Water recovery by nanofiltration (NF) from the high salinity brine is emerging as a promising technology to alleviate the water shortage. Thin film composite membranes with polyamide (PA) selective layer are the mainstream in the field of NF. Nevertheless, the trade-off between permeance and retention as well as the structural stability of the mainstream PA membrane still restrict their widespread application. Herein, a novel interlayered thin-film nanocomposite (TFNi) nanofiltration membrane was fabricated based on the interfacial polymerization. The PDA@MXene hybrid was employed as the interlayer to modulate the adsorption and diffusion process of amine monomers, giving rise to the formation of thin and rough PA selective layer, which could accelerate the transport of water molecules. Moreover, PM-TFNi membrane demonstrated higher crosslinking degree and more negatively charged surface, significantly benefiting the repulsion of inorganic salt ions. In this context, PM-TFNi membrane rendered a competitive permselectivity with the water flux of 18.3 L m−2 h−1 bar−1 and the Na2SO4 rejection of 98.0%. In addition, PM-TFNi membrane exhibited distinguished long-term stability and pH resistance. Overall, this work would provide a paradigm shift in designing high-performance and robust NF membrane for the water treatment.

Stochastic modelling of the instantaneous velocity profile in rough-wall turbulent boundary layers

The statistical properties of uniform momentum zones (UMZs) are extracted from laboratory and field measurements in rough wall turbulent boundary layers to formulate a set of stochastic models for the simulation of instantaneous velocity profiles. A spatiotemporally resolved velocity dataset, covering a field of view of $8 \times 9\,{\rm m}^2$ , was obtained in the atmospheric surface layer using super-large-scale particle image velocimetry (SLPIV), as part of the Grand-scale Atmospheric Imaging Apparatus (GAIA). Wind tunnel data from a previous study are included for comparison (Heisel et al., J. Fluid Mech., vol. 887, 2020, R1). The probability density function of UMZ attributes such as their thickness, modal velocity and averaged vertical velocity are built at varying elevations and modelled using log-normal and Gaussian distributions. Inverse transform sampling of the distributions is used to generate synthetic step-like velocity profiles that are spatially and temporally uncorrelated. Results show that in the wide range of wall-normal distances and $Re_\tau$ up to $\sim O(10^6)$ investigated here, shear velocity scaling is manifested in the velocity jump across shear interfaces between adjacent UMZs, and attached eddy behaviour is observed in the linear proportionality between UMZ thickness and their wall normal location. These very same characteristics are recovered in the generated instantaneous profiles, using both fully stochastic and data-driven hybrid stochastic (DHS) models, which address, in different ways, the coupling between modal velocities and UMZ thickness. Our method provides a stochastic approach for generating an ensemble of instantaneous velocity profiles, consistent with the structural organisation of UMZs, where the ensemble reproduces the logarithmic mean velocity profile and recovers significant portions of the Reynolds stresses and, thus, of the streamwise and vertical velocity variability.

Experimental investigation of productivity and surface integrity features in trim cut WEDM operation of hybrid metal matrix composite

Present study is focused on optimization of WEDM process parameters for increased productivity and improved surface quality of the machined surface of hybrid composite [Al6061 (90 %), SiC (2.5 %) and TiB2 (7.5 %)] by utilizing the trim cut strategy. Effects of four factors namely, pulse on time (Ton), peak current (Ip), wire offset (WO) and rough-cut history (RCH) have been investigated on response characteristics namely, material removal rate (MRR), surface roughness (SR) and Recast layer (RL) thickness; using Box-Behnken design (BBD) for the experimentation. Three levels of RCH i.e., high, medium and low have been included to investigate the effectiveness of trim cut strategy for dealing with rough-cut surface under varied conditions. The optimized parametric setting has been obtained for multiple responses using desirability function. RCH is found to be most significant factor for MRR, while pulse on time (Ton) is found most significant for SR and RL. WO has been found to play an important role in controlling the thickness of RL. It is observed that after trim cut, surface roughness is improved for experiments conducted under high and medium levels of RCH. However, almost no improvement in SR is obtained for low level of RCH. Trim cut strategy is also found to be effective in reducing the thickness of recast layer, however, it is noticed that the percentage reduction in recast layer thickness for samples machined under high level RCH is greater than that for the other two levels of RCH.

Effect of bath temperature on the efficiency and properties of Cu2O/ZnS/ZnO heterojunctions thin film prepared by electrodeposition and chemical bath deposition methods

A novel p-n type Cu2O/ZnS/ZnO heterojunction thin film was successfully fabricated by a combination of electrodeposition and chemical bath deposition techniques. The effect of bath temperature (T = 75, 80, 85, 90 °C) on the growth of ZnS layers was investigated. The influence of ZnS buffer layers on the properties and efficiency of the prepared heterojunction thin films were examined using XRD, FE-SEM, AFM, EDS, UV–Vis, and electrochemical measurements. The analysis of prepared films revealed that the Cu2O/ZnS/ZnO heterojunction exhibits a unique combination of hexagonal structure of ZnO and the cubic structure of Cu2O. It was found that all the heterojunction films exhibit the growth of composed pyramids and corner grains with a homogenous distribution. The optical band-gap of the deposited ZnS buffer layers decreased from 3.46 eV to 3.35 eV with an increase of bath temperature from 75 °C to 90 °C. Moreover, the obtained results revealed that the thicknesses and the surface roughness of ZnS buffer layers increased when bath temperature increased. Mott-Schottky results of the heterojunctions indicate a p-type semiconductor behavior for the Cu2O, while it was observed an n-type semiconductor behavior for the ZnO and ZnS layers. As a result, the photocurrent response of Cu2O/ZnO heterojunctions with ZnS layer insertion was enhanced from 0.175 to 0.730 mA, which can be attributed to the reduced electron transfer resistance, enlarged photo-generated (e−/h+) carrier separation efficiency, and enhanced light absorption due to the presence of ZnS buffer layers. These results highlight the advantages of the bath temperature on the deposition of ZnS for photoelectrochemical and solar cells applications.

Towards green membranes: Repurposing waste polypropylene with a single plant-based solvent via tandem spin-casting and annealing

A key aspect of advancing sustainable membrane technology is to source eco-friendly polymers, such as recycled plastic waste, use renewable plant-based solvents, and limit the number of solvents used in dissolution-precipitation processes. In this study, we upcycle polypropylene PP waste into bi-layered microporous superhydrophobic membranes using a single plant-based solvent, Cymene, through tandem spin-casting and annealing. The surface roughness and hydrophobicity of the top layer enhance selectivity, while the presence of micropores ensures efficient liquid passage and high permeability. The microporous bottom layer serves as a substrate for the top layer, providing structural support. Various annealing conditions were employed to optimize hydrophobicity, roughness, porosity and strength of as-prepared membranes, yielding high permeance and outstanding separation efficiency. The fabricated membranes were subjected to oil–water emulsion separations, demonstrating a contact angle exceeding 155° and a surface roughness of 123 nm, resulting in an organic solvent flux of 14,000 Lm-2h−1 with a 96 % water rejection. Tensile strength and strain % were found to be 13–28 MPa and 20–27 %, respectively. This research provided access to environmentally friendly membranes, adding value to plastic waste with potential benefits to both the polymer and membrane industries as they transition towards a circular economy.

Effects of thickness and roughness on plasmonic characteristics of gold thin films deposited on polished optical fiber

The thickness and roughness of metal layers substantially affect the performance of surface plasmon resonance (SPR)-based sensors. The deposition methods, control parameters, and substrate characteristics influence the layer thickness and roughness. This study investigates the SPR characteristics of a polished optical fiber surface coated with gold (Au) metal of different thicknesses. The Au layer is deposited via the thermal evaporation method, and its thickness is varied by controlling the deposition time (3–6 min). A proportionality relationship between thickness and deposition time is observed. Island-shaped structures in gold (Au) morphology are formed due to low adhesion to the substrate. The shape of this island creates gaps in the layer, causing scattering. In addition, the roughness on the gold surface triggers the Localized Surface Plasmon Resonance (LSPR) phenomenon. As a result, the measured dielectric characteristics differ from the reference. The SPR curve calculation simulation was carried out based on reference optical parameters and measurement results by an ellipsometer, which were then compared with experiments. The obtained results show that the substrate roughness, morphology, and thickness of the Au layer play an essential role in determining the characteristics of the SPR curve in a fiber optic plasmonic sensor. As a result, in basic experiments, the sample with an Au thickness of 27.37 nm (deposition time = 3 min) shows better characteristics (half-maximum full width, minimum transmittance, and resonance wavelength) compared with the sample with an Au thickness of 53.97 nm (deposition time = 4 min), Although 53.97 nm is the optimal thickness from the simulation using reference optical parameters (smooth substrate surface and smooth gold layer).

Preparation of a CPVC composite loose nanofiltration membrane based on plant polyphenols for effective dye wastewater treatment.

The textile industry's high-salinity wastewater presents a significant difficulty for fractioning salts and dyes. To fractionate the dyes and salts, a high-performance CPVC composite loose nanofiltration membrane (LNM) was fabricated by interfacial polymerization. The organic phase was obtained by crosslinking polyethylenimine (PEI) with tannic acid (TA) and gallic acid (GA) using TMC. The resultant composite LNM performance was enhanced by adjusting the coating parameters, which included TA and GA concentrations as well as coating time. The study examined the effects of the total content of TA/PEI and GA/PEI concentrations on the chemical structure, surface roughness, and microstructure of the selective layer of LNM using SEM, AFM, FTIR, and water contact angle measurements. It also investigated the filtration performance of the membrane's selective layer, including pure water flux, PEG800 rejection rate, and membrane fouling analysis. However, the resultant membrane treated simulated reactive black 5 (RB5) dye wastewater. When the total content of TA/PEI is 4 kg L-1, the permeability of pure water flux is high at 7.5 L per m2 per h per bar when the total content of GA/PEI is 14 kg L-1 and the pure water flux is high at 8.8 L per m2 per h per bar. The overall PEG800 rejection rates were 97-98.98%. The optimal TA : PEI ratios reached a good pure water permeability up to 6.4 L per (m2 per h per bar) with a high rejection rate of 99.69% for a ratio 1/3 to dye, and GA : PEI ratios reached a good water permeability at 5.5 and 6.5 L per (m2 per h per bar) with rejection rates of 99.21% and 98.88% for ratio 1/3 and 3.5/10.5 for simulated RB5 dye, and the NaCl retention rate gradually decreased from 4% to 3%. The resultant LNM demonstrated promising applications in dye and salt fractionation.

Experimental investigation of wire electrical discharge machining parameters on WE43 magnesium alloy

The influence of wire electrical discharge machining (WEDM) factors on the WE43 magnesium alloy is experimentally investigated in this work. Voltage, peak current, pulse-on time, and pulse-off time, are some of the factors taken into consideration in the study. The goal of the study is to understand how the output responses like material removal rate (MRR), surface roughness (SR), and development of recast layers are affected by the factors like voltage, peak current, pulse-on time and pulse-off time. The experimental set-up used a wire electrical discharge machine with a brass wire electrode and a workpiece made of the WE43 magnesium alloy. The L27 orthogonal array was used to alter the selected parameters through a series of experiments. The findings of the experimental investigation showed a strong link between the output responses and the electrical discharge machining (EDM) parameters. Peak current was discovered to have a direct correlation with the rate of material removal, with greater currents resulting in faster machining. SR and MRR were affected by pulse-on time and pulse-off time. Voltage had a direct impact on the development and thickness of the recast layer, with higher voltages favoring thinner recast layers.

Surface Modification of Magnesium Alloy AZ91D Using Nanopowder Mixed Electrical Discharge Machining for Biodegradable Implant.

Powder-mixed electrical discharge machining (PMEDM) enhances the effectiveness of the electric discharge machining process. It has been used on the Mg alloy AZ91D to address biodegradation concerns in implants. By combining nano-conductive powder particles with the dielectric fluid, PMEDM creates a functional surface. Process parameters like pulse on time, pulse off time, peak current, and powder concentration are examined to optimize material removal rate (MRR), surface roughness (SR), and white layer thickness (WLT). The optimization of input parameters was completed using the Taguchi L9 technique and further analyzed using ANOVA technique that illustrates Ton and pulse-off time as more significant process parameters for powder mixed electric discharge machining as compared with electric potential and peak current. The optimal surface roughness value is found to be 2.215 μm at 3A pulse current and 15 μs Toff time which suggest the material to be suitable for implants.

Investigation of Cu Doping Concentration on the Structural and Antimicrobial Properties of TiO₂ Thin Films

This study aims to examine the microorganism-fighting properties of the thin layers of TiO2. These TiO2 film as synthesized through a chemical process, in which different concentrations of copper have been added. The ability of films to inhibit the growth of different types of bacteria and fungi was examined using the disk diffusion technique. TiO2 films without additives exhibited mild antibacterial action, with inhibition areas varying according to the dose and type of microorganism. In contrast, the films that received a dose of copper showed significant increases in their ability to inhibit bacterial growth. More prominent detention areas were observed when a dose of 60 µg/mL and a doping concentration of 0.1% were used. According to X-ray diffraction tests, it was revealed that the thin films of TiO2 exhibit a cubic crystalline configuration, indicating their high crystallinity and the variation in the position of the peaks due to the inclusion of copper in their composition. The effectiveness in combating bacteria increased when the size of the crystals was raised from 6.72 nm (undoped) to 8.39 nm in presence of 0.1% copper. Significant changes occurred in the external appearance, as seen in the photographs taken using scanning electron microscopy (SEM). The modifications higher concentration of Cu doping, a transformation from smooth surfaces of pure ZnS to rough and porous layers in the films doped with Cu is observed. Specifically, the study reveals that by adding copper to thin films of zinc sulfide, their effectiveness can be enhanced, paving the way for the advancement of materials with antimicrobial properties.

Influence of stress-relieving heat treatments on the efficacy of Co-Cr-Mo-W alloy copings fabricated using selective laser melting.

Purpose This study aimed to evaluate the influence of stress-relieving heat treatments on the metal-ceramic bond strength and fitness accuracy of selective laser melting (SLM)-fabricated Co-Cr alloy copings.Methods SLM-manufactured Co-Cr samples were stress-relieved at 750 (Ht-750) and 1150 °C (Ht-1150). The microstructure, surface roughness, metal-ceramic bond strength, marginal and internal fit, Vickers hardness, and residual stress were then compared with those of the non-heat-treated group (As-built). The results were analyzed using one-way ANOVA and post-hoc tests (Tukey's or Student's t test) (P = 0.05).Results The microstructure of the Ht-1150 samples had a brittle oxide layer and lower surface roughness, resulting in significantly lower bond strength values than those of the other groups. The As-built group exhibited significantly lower marginal gap values than the Ht-750 and Ht-1150 groups. Therefore, the post-heat treatments degraded the marginal fitness. The surface residual stress in all sample groups were compressive because of the sandblasting effect. The compressive stresses were larger in Ht-1150 than in As-built and Ht-750 owing to their low hardness values.Conclusions Stress-relief annealing porcelain-fused-to-metal single crowns does not improve bond strength and degrades fitness accuracy because additional post-heat treatments induce thermal distortion. These findings are expected to facilitate the direct application of As-built SLM single crowns in dentistry to minimize post-manufacturing costs and time.

Stabilization of roughness parameters of rolls of temper mill during idle running in stand

The main results of improving in the condition of the surface layer of the working rolls of the training mill with their joint rotation pressed against each other in a state without a trained strip, are considered in order to further minimize changes in the roughness parameters of the trained strip from roll to roll. The analysis of changes in the roughness parameters of the working rolls during their running-in as a result of the elastic-plastic interaction of the microsteps of their surfaces is carried out. Mathematical dependences are obtained for calculating of the roughness parameters of the working rolls during their idle running in the stand, taking into account the ergodicity function of the process. It is shown that the permissible degree of reduction of the height parameters of the rough layer of the working rolls before stabilization during their running is determined by contact loads, physical and mechanical properties of the material of the rolls, the initial parameters of the microgeometry of their surfaces and friction conditions, and the time to stabilize of the roughness parameters depends mainly on the contact load and the speed of running-in, decreasing with decreasing load and increasing speed. It is determined that the maximum possible reduction in the initial roughness of the roll treated with shot after idle running them in a stand with a coefficient of friction of 0.3 is on average 57 %. A further change in roughness is associated with the effect of wear of the rough layer during the training of a cold-rolled strip. The obtained mathematical dependencies allow you to assign processing parameters, such as the compression force of the rolls, the speed or at a given speed — the running-in time.

Improved dry sliding wear behavior of TA1titanium by low-temperature plasma nitriding by CCPN method

Cathodic cage plasma nitriding (CCPN) has been proven a promising technique to improving titanium’s poor wear resistance at a relatively lower temperature. Nonetheless, less attention has been paid to the performance of the treated sample at the cathodic potential by CCPN process, mostly on the sample at the floating potential. It has been demonstrated that a nitrogen diffusion layer is formed other than compound layer at the cathodic potential, which is beneficial to improve the bearing-load capacity and adhesion strength between the modified layer and the substrate. In this study, a cathodic cage in combination with pulsed-biased system has been used to realize nitriding of TA1 titanium at the cathodic potential below 660 °C. The influence of pulsed current and treatment time on the resulting surface microstructure and wear performance when sliding against Si3N4 balls were studied. Results showed that with the increasing pulsed current and prolonged processing time, the nitride layer thickness, hardness and roughness also increase. Additionally, although the anti-wear resistance is considerably improved through nitriding treatment compared to untreated TA1 titanium, and there are still differences between the samples prepared under different nitriding parameters. Lastly, the optimum pulsed current and processing time of the CCPN process that provide the best tribological characteristics are determined.