Thickness Of Intermediate Layer Research Articles

Determination of Diffusion Coefficients of Nickel and Vanadium into Stainless and Duplex Steel and Titanium

When heterogeneous joints are created, problems with the formation of intermetallic phases arise. There are various ways to reduce the formation of intermetallics. One of the ways that is discussed in this article is to use a suitable interlayer of appropriate thickness when forming the joint. A too-thin interlayer does not protect against the formation of brittle intermetallic phases. On the other hand, a too-thick interlayer increases the heterogeneity of the joint and, thus, decreases its useful properties. Within this paper, the formation of diffusion joints between the base material (AISI 304 steel, duplex steel, AISI 316L steel, or titanium grade 2) and the 0.2 mm thick intermediate layer (nickel or vanadium) was studied. Initial diffusion joints were prepared in a Gleeble 3500 machine, and samples for the study of diffusion kinetics were subsequently heat-treated in a vacuum furnace. The result of the research was the determination of specific diffusion parameters of nickel and vanadium into all four tested base materials. The initial diffusion depth (simple heating to the target temperature without holding at this temperature) of nickel was 4.46 µm into duplex steel and 5.48 µm into Ti Gr. 2 at 950 °C. At the same temperature, the initial diffusion depth of vanadium was 14.54 µm into duplex steel and 14.32 µm into Ti Gr. 2. In addition, general equations for the calculation of diffusion coefficients for the mentioned materials in the temperature range of 850 to 1150 °C were established.

Full-scale experimental study on the smoke descent and stratification in a two-storey building with varying ventilation conditions

This paper presents a full-scale experimental research on the smoke descent and stratification in a two-storey residential building under the coupling influences of vertical connection channels and ventilation conditions. The two floors were connected by one atrium and one stair, and the fire source was located on the second floor. Wood crib and gasoline were selected as representative fuels to reflect typical residential fire scenarios, with heat release rates of 82 kW and 140 kW, respectively. The states of the building openings were varied to simulate different ventilation conditions. Results showed that the smoke tended to spread in the ridge direction due to the structural limitations of slope roofs. The temperature distribution in both the ridge and slope directions was obtained. A special “three-zone” smoke stratification structure including upper smoke layer, intermediate air layer and lower smoke layer is observed, which is significantly different from the well-known “two-zone” model. The “three-zone” stratification resulted in a nonmonotonic vertical temperature distribution in the atrium. The lower smoke layer thickness Zl,g was found to be greatly affected by ventilation conditions. Based on the boundary layer theories and the law of energy conservation, a series of expressions were established to calculate Zl,g and intermediate air layer thickness δw, which are the key parameters of the “three-zone” stratification. The theoretical calculations matched the experimental data well and explained the sharp trends of δw and Zl,g under different ventilation conditions. This study can provide theoretical guidance about fire detection, smoke exhaust and people evacuation in residential buildings.

Development of Laminated Egg-Shaped Tsunami Shelter Structure Made of Steel-Cushioning-Steel

When a tsunami is caused by an earthquake or other event, spherical shelters are developed to protect people from the tsunami. This study proposes a new egg-shaped laminated tsunami shelter with a buffer layer to improve the functionality of traditional spherical shelters. The inner and outer shells of this shelter are made from thin-walled stainless steel, using the integral hydro bulge forming (IHBF) process. The space between these two layers was filled with urethane foam, providing an elastic buffer. This resulted in a laminated egg-shaped structure designed for tsunami protection. To verify the proposed laminated egg-shaped tsunami shelter and its processing method, an egg-shaped shell with an external shape (length 660 mm, width 493 mm) was fabricated using a 1.0 mm thick stainless plate, and a laminated egg-shaped tsunami shelter with a 25 mm thick intermediate layer made of urethane foam was fabricated. The shape accuracy of the processed egg-shaped laminated tsunami shelter structure was measured, and the maximum error between the surface shape of the molded egg-shaped shell and the true egg shape was -4.13 mm, and the relative error to the maximum radius of the egg shape of 246.5 mm was -1.68%. In addition, to assess the buffering effect under external impact loads, acceleration sensors were attached to both the inner and outer layers of the fabricated egg-shaped laminated tsunami shelters. A hammer was used to apply an impact load to the outer layer, and the response acceleration values recorded by the sensors on both layers were compared. It was found that the response acceleration of the inner layer was 15.81% lower than that of the outer layer.

Theoretical study of the influence of GaOx interfacial layer on the GaN/SiO2 interface property

The spontaneous formation of a Ga-oxide (GaOx) intermediate layer at the GaN/SiO2 interface has been reported during the SiO2 deposition on the GaN substrate. In this study, we have performed first-principles calculations and unveiled atomic and electronic structures of the GaN/SiO2 interface with 1-nm thick GaOx intermediate layer. Our calculations show that the top-layer Ga atoms on the GaN side are terminated with the O atoms on the GaOx side, leading to the clean GaN/GaOx interface and the absence of the electronic state in the midgap region. However, strongly localized states, which are originated from O atoms lone-pair orbitals in the –GaOSi– local structures, emerge in the gap near the valence-band maximum of GaN. These in-gap states become hole traps in GaN MOS devices, leading to a degradation in device controllability and operational speed.

Electroluminescence from Silicon‐Based Light‐Emitting Devices with Erbium‐Doped Ta2O5 Films

The visible and near‐infrared (NIR) electroluminescence (EL) from the light‐emitting device (LED) based on the erbium (Er)‐doped Ta2O5 (Ta2O5:Er)/SiO2/Si structure is reported in this study. Wherein, an ≈10 nm thick SiO2 intermediate layer serves as an energy plateau for forming hot electrons, which initially transport from Si via trap‐assisted tunneling mechanism under sufficiently forward bias with the negative voltage connecting with Si. The hot electrons impact‐excite the Er3+ ions incorporated into the Ta2O5 host, leading to the Er‐related EL from the aforementioned LED. It is found that the 750 °Cannealed Ta2O5:Er films are desirable to act as the light‐emitting component. Despite that the Er‐related photoluminescence from the Ta2O5:Er film becomes stronger in turn with the Er‐doping content increasing from nominal 0.75, 1.5 to 3 mol%, it is the Ta2O5:Er film with Er‐doping content of nominal 1.5 mol% rather than 3 mol% that enables the LED to exhibit the strongest EL. Based on the EL lifetime measurement and the structural characterizations, it is believed that the enhanced non‐radiative interactions among the Er3+ ions and the substantial amorphousness of Ta2O5 host caused by the nominal 3 mol% Er‐doping are responsible for the weakened EL as mentioned above.

The diffusion kinetics and interaction between Al0.3CoCrNiFe HEAs and molten Zinc at 470 °C

The diffusive kinetics and interaction between Al0.3CoCrNiFe HEA and molten zinc at 470 °C were investigated using solid-liquid diffusion couple method in this paper. The results indicate that the thickness of the third intermediate layer (FeZn13) increases with the increasing of reaction time, which is expressed as a dynamic equation (d = 0. 11 t + 15.38). Fe, Cr, Co, and Ni uniformly diffuse from the HEA after 30 min. An Al-rich region is present between the third intermediate layer and the HEA, while Ni and Zn elements accumulate within the cracks of the third intermediate layer. The binding sequence of the elements in the diffusion process unfolds as follows: Ni is bonded to Zn, followed by Co to Zn, and finally Fe to Zn, with increasing reaction time. The diffusion kinetics and interaction between the HEA and zinc can provide a comprehensive understanding of the zinc corrosion process on HEAs.

The microstructure and mechanical properties of aluminum/steel welded joint with Ni foil interlayers by FSLW

Friction stir lap welding experiments between 6061 aluminum alloy plate and DP590 dual-phase steel plate were carried out. The effects of welding parameters and addition of Ni foil interlayers with different thickness on the microstructures and mechanical properties of the lap joints were investigated. The shear strength of the joint reached the maximum value of 6597 N and showed a mixed ductile-brittle fracture mode when the welding speed, the rotating speed and the thickness of the Ni foil intermediate layer were set to 100 mm/min, 900 rpm and 0.3 mm, respectively. A certain amount of beneficial plastic AlNi and FeNi3 intermetallic compounds are formed through the reaction of Al, Fe and Ni at the aluminum alloy/steel interface.

Fabrication of NiAl alloy hollow thin-walled component through hot gas forming of Ni/Al laminated tube and conversion process

The NiAl intermetallic compounds have higher service temperature and lower density than traditional Ni-based super-alloy. In this work, for overcoming the fabricating bottleneck of NiAl alloy hollow thin-walled component, a typical NiAl alloy square-section component was obtained by hot gas forming of NiAl laminated tube and conversion. Firstly, the Ni/Al laminated tubes with tight interfacial bonding between layers and considerable plasticity was prepared by controlling the thickness and distribution of intermediate layer (NiAl3 and Ni2Al3). Then, the hot gas forming behavior and micro-damage control method of the Ni/Al laminated square-section component were studied under different process parameters. Finally, the Ni/Al laminated square-section components were converted into NiAl alloy components at 1200 °C/1 h. The results show that the forming temperature and gas pressure loading rate are the key parameters for hot gas forming of Ni/Al laminated materials. At an optimal temperature, the micro-damage can be avoided and the fillet accuracy can be controlled by adjusting the strain rate through using different gas pressure loading rates.

Effect of the thickness of amorphous silicon intermediate layer on the thermal transport of silicon/diamond interface

The effect of the thickness of the amorphous silicon (a-Si) intermediate layer on the thermal transport of the Si/diamond heterointerface is investigated by using molecular dynamics simulations. It is found that the TBC of the Si/diamond heterostructure with a 0.5-nm-thick a-Si intermediate layer increases by more than 38 % in comparison with that of the Si/diamond without the a-Si intermediate layer. Meanwhile, the thermal boundary conductance (TBC) of Si/diamond decreases with the increasing thickness of an introduced a-Si intermediate layer. Furthermore, by examining the phonon vibrational spectrum, we found that introducing the a-Si intermediate layer at the interface between Si and diamond alleviates the phonon mismatch between Si and diamond, which increases the available heat transport channels and therefore leads to an increase in TBC. Finally, we observed that the TBC increases with the temperature of the Si/diamond heterostructure due to the enhancement of the inelastic scattering of phonons. These results indicate that the thermal transport of the Si/diamond heterointerface can be effectively regulated by controlling the thickness of the a-Si intermediate layer, which also provides further insight into thermal management design in Si/diamond-based electronic devices.

Molecular dynamics studies of the effect of intermediate Fe layer thickness on the enhanced strength and ductility of Cu/Fe/Ni multilayer

The synergistic strength-ductility is very important for composite materials. In this work, we studied the effect of intermediate layer thickness on the mechanical properties of Cu/Fe/Ni multilayer by introducing harder intermediate layer and non-coherent interface using molecular dynamics simulation, and revealed the relationship between the deformation mechanism and the strength-ductility from atomic scale. The results show that the yield strength and flow stress increase with increasing Fe layer thickness, but the tensile strain is opposite. Plastic deformation of all models are triggered by slipping of misfit partial dislocation originating from the decomposition of perfect dislocation on semi-coherent interface. However, the addition of Fe layer and non-coherent interface increases the resistance of dislocation crossing interface, and changes the dominant deformation mechanism from Shockley partial dislocation slipping to deformation twinning migration, thus improving the strength and ductility of multilayer. In addition, the evolution laws of the dislocation length and interface morphology as well as the shear strain distribution are discussed.

The microstructure and mechanical properties of aluminum/steel welded joint by FSLW

Friction stir lap welding experiments between 6061 aluminum alloy and DP590 dual-phase steel plates were carried out. The effects of welding parameters and the addition of Cu foil interlayers with 0–0.3 mm thickness on the microstructures and mechanical properties of the lap joints were investigated. The shear strength of the joint reached the maximum value of 5337 N and showed a mixed ductile-brittle fracture mode when the welding speed, the rotating speed, and the thickness of the Cu foil intermediate layer were set to 80 mm/min, 900 rpm, and 0.1 mm, respectively. The plastic Al2Cu and AlCu intermetallic compounds formed through Al and Cu reaction at the aluminium alloy/steel interface play a beneficial role in the Cu-added joint strength.

Machine learning approach to model and predict the shear strength of TZM-graphite joint bonded by spark plasma sintering

These days, the study of titanium alloys has grown into a sizable topic of study. Due to its remarkable high-temperature applications, titanium zirconium molybdenum (TZM) is one such alloy with considerable research potential. In this study, the shear strength of TZM-graphite alloy, which was bonded using the spark plasma sintering (SPS) process with titanium foil as an interlayer, has been predicted using a machine learning approach. The shear strength of the TZM-graphite alloy depends on various process parameters such as sintering temperature, sintering pressure, holding time, and intermediate layer thickness. Since the correlation between input variables and output variables is intricate and non-linear, an artificial neural network (ANN) model was developed in this research to investigate the relationship between bonding parameters and the shear strength of the TZM-graphite joint. The feed-forward backpropagation neural network was utilized for training the model and predicting the shear strength. By computing the Mean square error (MSE) and Average error (AE), the optimum number of neurons in the hidden layers was determined. Consequently, the model with 4–9-9–1 architecture was constructed, and its accuracy was assessed by contrasting the values obtained by the neural network with actual experimental data. The model was then validated using a variety of performance measuring indicators such as mean absolute percentage error (MAPE) and root mean square error (RMSE). The achieved correlation coefficient (R-value) of 0.99614% demonstrates that the proposed ANN model is an excellent fit for the experimental data to predict the accurate shear strength of the TZM-graphite joint. For further understanding of the influence of input parameters on the shear strength of the TZM-graphite joint, 2D and 3D surface graphs were plotted.

Electroluminescence from Silicon-Based Light-Emitting Devices with Erbium-Doped ZnO Films: Strong Enhancement Effect of Titanium Codoping.

We report on the visible and near-infrared electroluminescence (EL) from the light-emitting device (LED) based on the erbium (Er)-doped ZnO (ZnO:Er)/SiO2/n+-Si heterostructure, wherein an ∼10 nm thick SiO2 intermediate layer serves as the energy plateau for producing hot electrons, which come from n+-Si via the trap-assisted tunneling mechanism. These hot electrons excite the doped Er3+ ions by inelastic collision, enabling the Er-related EL from the aforementioned LED. More importantly, by means of codoping the appropriate content of titanium (Ti) into the ZnO:Er film, the aforementioned Er-related emissions can be significantly enhanced. The density functional theory calculations indicate that the Ti-codoping improves rather than degrades the symmetry of the crystal field around the optically active Er3+ ions, hence not increasing the intra-4f transition probabilities of Er3+ ions. However, it is found that Ti-codoping nearly eliminates the segregation of Er3+ ions near the ZnO/SiO2 interface. Moreover, Ti-codoping is derived to result in a number of Zn vacancies, which provide the sites for incorporating Er3+ ions in the ZnO matrix. For the above two reasons, the Ti-codoping promotes the incorporation of optically active Er3+ ions into the ZnO matrix, thus enhancing the EL from the aforementioned LED.

Efficiency enhancement of Cu2ZnSn(S, Se)4 solar cells by addition a CuSe intermediate layer between Cu2ZnSn(S, Se)4 and Mo electrode

A CuSe intermediate layer (IL) is prepared between CZTSSe and Mo electrode to decay the carrier recombination on the rear surface of the CZTSSe absorber. The power conversion efficiency (PCE) can be increased from 7.52% to 10.09% by optimizing the thickness of CuSe IL. The increased PCE comes from improvement in filling factor (FF), short-circuit current density (JSC), and open-circuit voltage (VOC), and their contribution percent is calculated to be 63.08%, 24.83%, and 12.09%, respectively. It is demonstrated that boosted FF is mainly due to decreased reverse saturation current density (J0), raised JSC owing to higher photogenerated current density (JL), and enhanced VOC caused by decreased J0 and higher JL. The contribution percent of (ideal factor (A), J0), JL, Rs, and shunt resistance (Rsh) to increased PCE is calculated to be 60.84%, 27.41%, 10.33%, and 1.42%, respectively. By experimental characterization and SCAPS-1D simulation, it is suggested that decreased J0 results from the formation of passivation field and high electron potential barrier at the rear surface of CZTSSe due to the addition of suitable thickness CuSe IL, higher JL from the increase in width of the depletion region of CZTSSe/CdS, lower Rs from decrease in thickness of Mo(S, Se)2, and bigger Rsh from improved crystal quality of CZTSSe absorber.

Atlantic Cod Growth History in Flemish Cap Between 1981 and 2016: The Impact of Fishing and Climate on Growth Performance

Flemish Cap cod collapsed in the early 90’s after facing multiple threats due to climate variability and anthropogenic pressures. A master 35-year cod growth chronology was reconstructed in the present study by using sclerochronology techniques. Three additional chronologies were developed to account for the age-dependent effect of maturity and fishing intensity on growth. All chronologies showed that cod growth has decreased over the years and it is currently at the minimum level in the historic of data series. Hierarchical mixed-effects models were applied to the master chronology to identify extrinsic drivers of growth. The master chronology was divided into 3 periods: Premoratorium (1988-1998), Moratorium (1999-2009), and Postmoratorium (2010-2019). Our results showed that drivers of cod growth in the Flemish Cap varied between periods (Premoratorium: bottom temperature and fishing mortality, Moratorium: cod and pandalus abundance, and Postmoratorium: cod abundance and thickness of the cold intermediate layer). Our results suggest that density-dependence processes, food availability, and global warming may be behind the lack of recovery of the Flemish Cap cod stock. The Flemish Cap cod growth chronology shows variations on growth over time and identifies its drivers, having the potential to be included in the NAFO stock assessments or to be used to set dynamic reference points that guarantees the stock sustainability.

High efficiency of broadband transmissive metasurface terahertz polarization converter

Terahertz wave is between microwave and infrared bands in the electromagnetic spectrum with the frequency range from 0.1 THz to 10 THz. Controlling and processing of the polarization state in terahertz wave are the focus due to its great influence on the characteristics. In this paper, a transmissive metasurface terahertz polarization converter is designed in 3D structure with an upper surface of ruler-like rectangular, an intermediate dielectric layer and a lower surface of metal grid wires. Numerical simulations of the converter show that the polarization conversion ratio (PCR) is above 99.9% at 0.288 THz–1.6 THz, the polarization rotation angle (PRA) is close to 90° at 0.06 THz–1.4 THz, and the ellipticity angle (EA) is close to 0° at 0.531 THz–1.49 THz. The origin of the efficient polarization conversion is explained by analyzing the electric field intensity, magnetic field intensity, surface current, electric field energy density, and magnetic field energy density distributions of the converter at 1.19 THz and 0.87 THz, which are consistent with the energy transmittance and transmittance coefficient. In addition, the effects of different thickness and material of intermediate layer, thickness of upper surface material, polarized wave incidence angle, and metasurface materials on the performance of the polarization converter are discussed, and how they affect the conversion performance of the polarization converter are also explained. Our results provide a strong theoretical basis and technical support to develop high performance transmission-type terahertz polarization converters, and play an important role to promote the development of terahertz science and technology.

Transformations of the Microstructure and Phase Compositions of Titanium Alloys during Ultrasonic Impact Treatment Part II: Ti-6Al-4V Titanium Alloy

Experimental and theoretical studies enabled the reveal of patterns of the microstructure formation in the surface layer of Ti-6Al-4V titanium alloy subjected to ultrasonic impact treatment. The mixed amorphous and nanocrystalline structure of the 200 nm thick uppermost surface layer of titanium dioxide TiO2 was demonstrated using transmission electron microscopy. The 5 µm thick intermediate layer containing nanocrystalline α grains, and the 50–60 µm thick lower layer containing fragmented α-Ti grains with retained β phase were also observed. The refinement of the β-Ti phase during ultrasonic impact treatment was accompanied by the formation of the orthorhombic (α″) martensitic phase. Molecular dynamics simulation of strains of a vanadium-doped titanium crystallite subjected to ultrasonic impact treatment revealed the formation of striped dislocation substructures as well as the development of reversible β→α phase transformations. Ab initio calculations of the atomic structure of V-doped Ti crystallites containing α, β or α″ phases of titanium were carried out. On the basis of the results of the experimental observations, a molecular dynamics simulation and ab initio calculations a mechanism was proposed, which associated the development of the strain-induced β→α″ phase transformations in Ti-6Al-4V alloy with the presence of oxygen. The role of the electronic subsystem in the development of the strain-induced phase transformations was discussed.

Fabrication of β-Ga2O3/Si heterointerface and characterization of interfacial structures for high-power device applications

In this work, we fabricated Ga2O3(001)/Si(100) and Ga2O3(010)/Si(100) heterointerfaces by surface activated bonding at room temperature and investigated the effect of Si thickness on the thermal stability of the heterointerfaces by heating the bonding samples at different temperatures. The heterointerface with a thin Si exhibited a good thermal stability at 1000 °C. A 4 nm thick intermediate layer with a uniform thickness was formed at the as-bonded Ga2O3(001)/Si(100) heterointerface, but for the as-bonded Ga2O3(010)/Si(100) heterointerface, an intermediate layer with a non-uniform thickness was formed. The thickness of both intermediate layers ranged from 3.6 to 5.4 nm and decreased after annealing at 500 °C, followed by an increase after annealing at 1000 °C. The component of the intermediate layer includes Ga, O, and Si atoms.

Effect of temperature on the slag/refractory interfacial reaction with directed reduced iron (DRI) addition in an electric arc furnace (EAF) process: Diffusional growth of magnesiowüstite layer by Boltzmann-Matano analysis

This study investigated the effect of temperature (1550–1650 °C) on the electric arc furnace (EAF) slag and magnesia refractory interfacial reaction with 20% direct reduced iron (DRI) addition as an alternative iron source in an Ar atmosphere. Variations in MgO content from initial to final stage were proportional to the temperature, indicating that MgO degradation by molten EAF slag was affected by the concentration gradient between initial and saturation conditions depending on temperature. In addition, the temperature affected MgO content more dominantly than DRI did. In other words, temperature control in an EAF process using DRI is relatively more important than the control of DRI itself for preventing MgO refractory degradation. The magnesiowüstite (MW) intermediate layer thickness and MgO refractory dissolution depth increased as the temperature increased because MgO solubility in molten EAF slag is proportional to temperature. Finally, the inter-diffusivity (D˜Fe−Mg, m2/s), which was estimated by Boltzmann-Matano analysis, ranged D˜Fe−Mg=10−12.0−10−12.5 and logD˜Fe−Mg generally decreased with decreasing temperature. The activation energy was found to be approximately 240 kJ/mol. Therefore, it can be concluded that suitable control of temperature in an EAF process using DRI is important to minimize refractory degradation.

The shifting mosaic of ice-wedge degradation and stabilization in response to infrastructure and climate change, Prudhoe Bay Oilfield, Alaska, USA

We studied processes of ice-wedge degradation and stabilization at three sites adjacent to road infrastructure in the Prudhoe Bay Oilfield, Alaska, USA. We examined climatic, environmental, and subsurface conditions and evaluated vulnerability of ice wedges to thermokarst in undisturbed and road-affected areas. Vulnerability of ice wedges strongly depends on the structure and thickness of soil layers above ice wedges, including the active, transient, and intermediate layers. In comparison with the undisturbed area, sites adjacent to the roads had smaller average thicknesses of the protective intermediate layer (4 cm vs. 9 cm), and this layer was absent above almost 60% of ice wedges (vs. ∼45% in undisturbed areas). Despite the strong influence of infrastructure, ice-wedge degradation is a reversible process. Deepening of troughs during ice-wedge degradation leads to a substantial increase in mean annual ground temperatures but not in thaw depths. Thus, stabilization of ice wedges in the areas of cold continuous permafrost can occur despite accumulation of snow and water in the troughs. Although thermokarst is usually more severe in flooded areas, higher plant productivity, more litter, and mineral material (including road dust) accumulating in the troughs contribute to formation of the intermediate layer, which protects ice wedges from further melting.