Thermal Properties Of Substrate Research Articles

Hybrid manipulation of inkjet-printing deposition pattern of high particle concentration droplet by means of thermal and binary solvent effects

Inkjet-printing of functional material is a well-known drop-on-demand technology used in a wide range of modern applications, such as flexible electronics, biomedical testing, etc. It enables to deliver small amount of materials as ink to the specific location on target substrates. However, it is challenging to precisely manipulate the particle deposition characteristics which is crucial to the quality of the fabricated device. Unlike the traditional passive methods by manipulating the nanoparticle, solvent or substrate surface condition, we propose a passive-active hybrid manipulation method by employing a binary mixture solvent and heating substrate. In this paper, the effects of the solvent mixing ratio, the substrate temperature, the substrate thermal properties on the deposition characteristics of high concentration ITO nano-ink were investigated. Interestingly, we have observed a transition of the classic slim coffee-ring to a fat coffee-ring with a large ring width. A dimensionless number was developed to predict the transition boundary from fat-ring pattern to slim-ring pattern. Finally, the phase diagrams of deposition patterns on three substrates were developed, which were convenient for deposition pattern manipulation in real applications.

Ultrafast hot-carrier dynamics in ultrathin monocrystalline gold

Applications in photodetection, photochemistry, and active metamaterials and metasurfaces require fundamental understanding of ultrafast nonthermal and thermal electron processes in metallic nanosystems. Significant progress has been recently achieved in synthesis and investigation of low-loss monocrystalline gold, opening up opportunities for its use in ultrathin nanophotonic architectures. Here, we reveal fundamental differences in hot-electron thermalisation dynamics between monocrystalline and polycrystalline ultrathin (down to 10 nm thickness) gold films. Comparison of weak and strong excitation regimes showcases a counterintuitive unique interplay between thermalised and non-thermalised electron dynamics in mesoscopic gold with the important influence of the X-point interband transitions on the intraband electron relaxation. We also experimentally demonstrate the effect of hot-electron transfer into a substrate and the substrate thermal properties on electron-electron and electron-phonon scattering in ultrathin films. The hot-electron injection efficiency from monocrystalline gold into TiO2, approaching 9% is measured, close to the theoretical limit. These experimental and modelling results reveal the important role of crystallinity and interfaces on the microscopic electronic processes important in numerous applications.

Femtosecond fiber laser-induced surface structuring of metals at cryogenic temperatures

Creating nano/micron-sized topographies on metal surfaces holds great promise across many optical, biomedical, and industrial applications. Among the most effective and widespread techniques for producing precisely organized features on material surfaces is laser-induced periodic surface structuring (LIPSS). Herein, we utilize a femtosecond fiber laser to generate LIPSS on low- and high-thermal-conductivity materials under extremely low temperature conditions, and we compare the results with those achieved at room temperature. To the best of our knowledge, this is the first instance of conducting laser-induced surface structuring experiments under cryogenic conditions. We examine how the initial thermal conditions of the substrate affect the patterns that form on its surface. Different surface characteristics emerge based on the substrate's thermal properties and the intensity of the laser beam. For instance, when we subject a silver substrate (known for high thermal conductivity) and tungsten substrate (known for high melting point) to laser-induced surface structuring at a low temperature of 110 K, they develop high-spatial frequency ripples on the surface oriented parallel to the polarization direction of the laser with a periodicity of around 100 nm, which is one-tenth the wavelength of the irradiating laser (1030 nm). In contrast, the cooled stainless-steel substrates (known for low thermal conductivity) exhibit no alterations in the patterns or their periodicity compared to substrates structured at room temperature. Furthermore, the formation of well-defined LIPSS patterns continue to persist on the surface of the cooled copper substrate, even when using large number of laser pulses. However, there exist specific localized regions of increased energy that disrupt the uniformity of the LIPSS pattern formation when the process is carried out at room temperature.

Influence of environment on self-propagating reactions in Al/Ni multilayer foils

Reactive aluminum–nickel multilayer system shows exothermic energetic materials which act as a heat source for packaging and bonding of microsystems. The main challenge is controlling the self-propagation reaction velocity and temperature generated by thermal management through different thermal conductive substrate materials. The current work investigates the heat distribution of Al/Ni multilayer foils from different thermal conductive substrates which act as heat sink materials during the self-propagating reaction. A two-dimensional numerical model was developed to study thermal conductive heat loss and substrate thermal properties on the self-propagating reaction in Al/Ni multilayer foils. The self-propagating reaction was introduced on the surface of the foils by an electrical spark. Here we investigate the minimum critical thickness of Al/Ni multilayer foils which shows the self-propagation reaction on different substrates and verified from the two-dimensional numerical model. The outcomes of this investigation will facilitate the integration of Al/Ni multilayer foils on different substrates as intrinsic heat sources for different applications of micro/nanodevices.Graphical abstract

From impact to solidification in drop-on-demand metal additive manufacturing using MetalJet

Drop-on-demand metal jetting is a promising additive manufacturing (AM) technology that is gaining interest due to its capability to directly print complex single and multi-material components at high resolutions. It also has key advantages over other metal AM techniques, such as avoiding powder handling and extensive post-processing. In this method, parts are built via spatially controlled deposition of individual molten droplets onto a substrate. Therefore, the success of the process entirely depends on the behaviour of these single droplets from deposition to solidification including their interactions with the substrate, which is scarcely investigated to date. To fill this research gap, the in-house MetalJet platform was used to investigate the spreading and solidification of metallic micro-droplets at low Weber numbers. This was undertaken onto various substrates using a range of jetting and substrate temperatures through an integrated experimental, analytical, and computational approach. This study reports that increasing the substrate temperature enhanced the diffusion between the droplet and substrate, hence improving the bonding. Moreover, ripples forming on a droplet’s periphery during solidification disappeared at elevated substrate temperatures, resulting in improved inter-droplet bonding. Furthermore, the significant role of the substrate wettability and thermal properties, which control the droplet’s dynamics and solidification behaviour, respectively, is elucidated. This highlights the importance of substrate material selection using this technology. The results presented in this article underpin the optimal process conditions under which the 3D structures produced with this technology can exhibit reliable integrity and consistency. This represents a step forward in the direct metal printing of high resolution functional multi-material components.

Contact Line Catch Up by Growing Ice Crystals

The effect of freezing on contact line motion is a scientific challenge in the understanding of the solidification of capillary flows. In this Letter, we experimentally investigate the spreading and freezing of a water droplet on a cold substrate. We demonstrate that solidification stops the spreading because the ice crystals catch up with the advancing contact line. Indeed, we observe the formation and growth of ice crystals along the substrate during the drop spreading, and show that their velocity equals the contact line velocity when the drop stops. Modeling the growth of the crystals, we predict the shape of the crystal front and show that the substrate thermal properties play a major role on the frozen drop radius.

Thermal Swing Evaluation of Thermal Barrier Coatings for Diesel Engines

“Thermal swing” coatings have recently been of great interest to automotive researchers for their potential to insulate internal combustion engines, reduce cooling requirements, and increase their efficiency. Plasma-sprayed yttria-stabilized zirconia, ceramics in the MgO-Al2O3-SiO2 system (cordierite, mullite, and steatite), and silicate-yttria-stabilized zirconia composite thermal barriers have been investigated in this context with thermophysical properties measured using a thermal flash method and further screened by thermal swing using a custom laboratory developed functional test. Correlations between microstructure and thermal properties are developed and their combined impact on thermal swing assessed. The coatings thermal effusivity dominates these considerations for coatings above the characteristic thermal diffusion length of periodic exposure, with substrate thermal properties quickly becoming important below this thickness. Plasma-sprayed cordierite and its composites are determined to be the most promising materials for this application, exhibiting the highest thermal swing and effusivities as low as 373 Ws1/2/m2K. Performance testing in a heavy-duty single-cylinder diesel engine is ongoing with preliminary data suggesting that thermal swing alone may not provide efficiency benefits. Coating thickness, roughness, and dynamic interactions in the engine may play a role in this, highlighting that many potential nuances need consideration for the successful applications of these coatings.

A direct method for the simultaneous characterization of thermal diffusivities of a bi-layer material consisting of a thin coating deposited on a substrate

This work presents a method dedicated to the simultaneous identification of the thermal diffusivities of coatings or thin film materials. To ensure non-destructive thermal characterization of the coating, the present method also implies the identification of the substrate thermal properties, which may be orthotropic. The estimation of thermal diffusivities is based on the resolution of an inverse problem by minimizing the quadratic difference between the response of a 3D semi-analytical model and the measurements resulting from a single ‘3D flash method’ type experiment, using a stochastic based optimization algorithm. A unique non-intrusive test, that consists in recording the temperature change cartography on one face of the sample by means of an infrared camera, is required. The evolution of the temperatures within the material is generated by a non-uniform and almost instantaneous excitation imposed by a CO2 laser on the measured face. The difficulties related to the control of the excitation, in terms of the distribution of the imposed flux or the energy absorbed by the material, are overcome by estimating the parameters associated to the excitation simultaneously with the thermal diffusivities. The developed method is applied to estimate the thermal diffusivity of a coating used in thermographic phosphor thermometry to measure wall surface temperatures and heat fluxes in combustion environments. The method is first evaluated on simulated data as a function of the measuring/excitation face in order to ensure the feasibility, the robustness and accuracy of the current method and to establish the best experimental configuration. Experimental results are then exploited and the estimation results are compared with other methods results.

Effect of Glass Substrate on the Film Properties of Poly Silicon by Excimer Laser Annealing

This work studies the effect of glass substrate thermal properties on the crystallization behavior and surface topography of polycrystalline silicon (poly-Si) films formed by a XeCl excimer laser annealing of amorphous silicon. Films of 60 nm hydrogenated amorphous silicon (a-Si:H) film were deposited on different glass substrates of varying thermal properties. A 500 nm SiO2 buffer layer was in between the glass and the silicon film. The silicon was crystallized by a XeCl excimer laser. The atomic force microscopy (AFM) and in-plane X-ray diffraction (IPXRD) were used to evaluate the surface topography, the surface roughness, and crystalline in-plane orientation of poly-Si, respectively. Grazing incidence X-ray diffraction (GIXRD) was employed to quantify the residual stress in poly-Si film. The film properties of poly-Si exhibit a small relationship with the glass thermal properties. The higher thermal conductivity of glass retards the poly-Si <111> texture and reduced the residual tensile stress. The higher thermal diffusivity of the glass causes a decline in the poly-Si <111> texture, the surface asymmetry and flatness. A light shield introduced between glass and buffer layer in the low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) structures, further weakens the impact of the glass substrate on excimer laser annealing (ELA) poly-Si properties.

Structural, Thermal, and Mechanical Properties of Spent Mushroom Substrate (SMS) and Rubberwood Sawdust (RWS) Binderless Particleboards

Structural, Thermal, and Mechanical Properties of Spent Mushroom Substrate (SMS) and Rubberwood Sawdust (RWS) Binderless Particleboards

Effect of Glass Substrate on the Film Properties of Poly Silicon by Excimer Laser Annealing

This work studies the effect of glass substrate thermal properties on the crystallization behavior and surface topography of polycrystalline silicon (p-Si) films formed by a XeCl excimer laser annealing of amorphous silicon. 60 nm hydrogenated amorphous silicon (a-Si:H) film was deposited on different glass substrates of varying thermal properties. A 300 nm SiO2 buffer layer was in between the glass and the silicon film. The silicon was crystallized by a XeCl excimer laser. The film properties of p-Si exhibit a small relationship with the glass substrate thermal properties. The higher thermal conductivity of glass retards the poly-Si <111> texture and reduced the residual tensile stress. The higher thermal diffusivity of the glass substrate causes a decline in the p-Si <111> texture, the surface asymmetry, and flatness.

Evaporation of a sessile water droplet during depressurization

This paper reports an experimental and theoretical study of sessile water droplet evaporation during depressurization. During the experiments, three kinds of surfaces were used: copper, slide glass and Teflon. The change in droplet shape with ambient pressure was recorded. The experimental results showed that the water droplet evaporated the fastest on the slide glass surface and the lowest on the Teflon surface, due to the different wettability of substrates. Bubbles were easily formed on the Teflon surface, and the existence of bubbles hindered the contraction of the contact line. A mathematical model was then developed to simulate droplet evaporation on the copper surface and the slide glass surface during depressurization, which combined the effects of air flow, the substrate thermal properties, evaporative cooling, internal circulation and the Stefan flow for the first time. The calculated results matched well with the experimental results, and the deviations between them were within 30%. A significant difference between sessile droplet evaporation under reduced pressure and under atmospheric pressure was that the droplet height did not follow the linear change with time, which was related to the change of droplet surface temperature. And then, the changes of droplet surface temperature and substrate surface temperature with time were analyzed based on calculations. Finally, the main factors affecting the accuracy of present model were proposed.

Interaction of advancing contact lines with defects on heated substrates.

We consider an advancing contact line traveling over a region of locally modified wetting or thermal substrate properties. A lubrication-type model is developed to account for coupling of viscous flow, evaporation, surface tension, and disjoining pressure. Stick-slip-type behavior is found for a range of conditions as the contact line passes over the defect and explained by a temporary increase in the local stresses disrupting the liquid supply into the contact line region. A simple estimate of the degree of contact line slowdown is obtained and compared with the numerical simulation results. Tangential stresses arising from the action of the electric field on the interfacial changes are accounted for in our model; neglecting them would lead to an overprediction of the time of interaction between the contact line and the defect. Increasing the substrate temperature uniformly has little effect on contact line motion, but local increase of the temperature enhances the tendency of the contact line to be pulled back by the defect, an effect explained by the Marangoni stresses.

Application of the inverse method in the 3 ω method for measuring the thermal conductivity of thin films

Planar nano-materials generally refer to samples that are extremely thin in the direction of thickness, such as nanofilms, graphene, and superlattice. They are of great importance in various fields, including transistors, thermoelectrics, and optoelectronics, etc. In practice, materials’ thermal transport characteristics often play a crucial role in applications. More importantly, due to the confinement in the direction of thickness, the mechanisms of thermal transport process in planar nano-materials become very different from those at the macroscale. For example, the effective lattice thermal conductivities of nanofilms are always highly dependent on their thickness, since phonon coherence, ballistic transport, and boundary scattering effects could occur in this case. Therefore, probing thermal transport properties of planar materials has been a research hotspot in both the research and industrial communities. The 3 ω method has been proven to be a powerful tool that can measure the thermal conductivities of planar materials effectively. Particularly for a thin film on a substrate, the differential 3 ω method was developed. In this scheme, it is necessary to determine the thermal properties of substrate materials in the first step. Thus, a reference sample should be measured in addition to the target sample, which not only increases the complexity of measurement but also reduces the measurement accuracy of the thin film’s thermal transport properties. In the present work, we used the numerical simulations to demonstrate that in the 3 ω method the combination of finite element method (FEM) and inverse problem method can derive the thermal properties of thin film and substrate simultaneously. It was found that the thermal conductivities could be determined accurately despite the cutoff frequency of measurement, whereas the thermal diffusivities’ accuracy could be improved with increasing cutoff frequency of measurement. Furthermore, as a test, the thermal conductivities of silicon dioxide (SiO2) thin film on the silicon (Si) substrate were measured using the method above. In our experiments, the thickness of Si substrate was 450 μm, and the thickness of SiO2 thin film was 950 nm. The frequency of driving current was set from 100 to 5000 Hz (the cutoff frequency). The trust region reflective method was adopted in the fitting process. Moreover, it was found that the measurement uncertainty of temperature rise was less than 1% and thus its influence on the uncertainties of measured thermal properties could be ignored. As a result, the major uncertainties of thermal conductivity measurement came from measuring the thickness of SiO2 thin film. The thermal conductivity of Si substrate was 142.1 W/(m K) with a relative error equal to approximately 2%, and the thermal conductivity of SiO2 thin film was 1.01 W/(m K) with a relative error equal to approximately 2%, which could agree well with the reported value in literature. In summary, the present work demonstrated that the combination of FEM and inverse method could be employed for thermal properties measurement, and thus analytical models are not always necessary. For future work, the methodology presented in this paper can be extended to deal with the measurement of thermal transport properties of irregular-shape thin flakes on a substrate.

Modelling for prediction of time-varying heat partition coefficient at coated tool-chip interface in continuous turning and interrupted milling

Knowing heat partition coefficient at tool-chip interface is important for accurate estimating the distribution of heat flux and temperature field in metal cutting process. The heat partition coefficient in steady metal cutting has been widely analyzed. However, the time-varying effect of heat partition coefficient is rarely investigated in metal cutting with coated tool. In this research, a novel model for prediction of the transient heat partition coefficient at coated tool-chip interface was proposed. The time-varying heat partition coefficient was quantitatively calculated. The new proposed model fully considered the coating thickness and material thermal properties compared with current models including Shaw's model, Kato-Fujii's model and Reznikov's model. The time-varying heat partition coefficients in continuous turning and interrupted milling process were comparatively analyzed. Results showed that the time needed for attaining quasi-steady-state of heat partition was about tens of milliseconds. The heat partition coefficient was mainly dependent on tool coating and workpiece thermal properties rather than tool substrate thermal properties. The heat partition coefficient was decreased with the increase of interrupted cutting speed. The new proposed model was verified accurate compared with former research and cutting experiment. The proposed methodology can guide for design and selection of coated tool in metal cutting production.

Simulating Heat Transfer During Transient Dropwise Condensation on a Low-Thermal-Conductivity Substrate.

The instantaneous heat-transfer performance of a surface is dictated by the number and sizes of drops on the surface. While performance averaged over longer times is of interest from a technology standpoint, accurate simulation of the transient state is important in condenser design because the maximum heat rejection of the surface occurs in this range. Steady-state dropwise condensation can be thought of as a collection of transient dropwise condensation cycles occurring in parallel. Traditional simulation of dropwise condensation has focused on making comparisons with experimental drop-size distributions at later times, after the process has reached a statistical stationary phase where the heat transfer is lower. Understanding how to model and simulate transient dropwise condensation where a maximum in heat transfer occurs will help us design higher heat-rejecting surfaces. Additionally, a constant temperature difference between the steam and the surface below the drop is assumed. While often valid, there are some cases where this is not valid, and measuring the drop growth rate is required. We report a way to simulate transient dropwise condensation using a measured population averaged drop growth rate. The simulation reasonably predicts the time evolution of the number density of drops, fractional coverage, normalized condensate volume, and median drop radius for pendant mode dropwise condensation experiments on a cooled, horizontal, dodecyltrichlorosilane-coated glass surface. It was also found that assuming a constant temperature difference grossly underpredicts the heat transfer. Modification of the single-drop heat-transfer model to include substrate conduction and a thermal boundary layer shows that in the limit of low thermal conductivity the drop growth rate is constant for large drops. Additionally, a comparison between experiments and simulation shows that condensation might be initialized by nucleation onto fixed sites and then transitions to random nucleation as more sites become activated and more favorable. Understanding how a substrate's thermal properties affect the progression of dropwise condensation is important in determining the removal performance of the surface. With the commercialization of 3D printing, it is possible to fabricate low-cost, lightweight, plastic substrates with physical texturing for condensation applications where mass and cost savings are critical.

Thermal Properties of Carbon Fiber-Reinforced Lightweight Substrate for Ecological Slope Protection

A new ecological substrate is proposed to achieve a desired electric conduction and heating to protect the slope plants from freeze injury. Expanded polystyrene (EPS), cement, carbon fiber, graphite, and raw soil are the main components of the ecological substrate. The electrical conductivity, heating efficiency, thermo-sensitivity, and heat preservation of the substrate are experimentally investigated. The result shows that the addition of carbon fiber could significantly decrease resistivity of substrate, but the effect of fiber content exceeding 3% on the resistivity of substrate becomes insignificant. Conductive fine materials (i.e., carbon fiber and graphite powder) covering the surface of EPS would result in a significant reduction of the global resistivity of non-dry substrate, but it could only slightly affect the counterpart of the completely dry substrates. The substrate could hardly be formed when the EPS content exceeds 4%. As EPS content increases, the contact surface decreases and the resistivity of the substrate increases. The peak temperature at 30 min of substrate without root is higher than that of substrate with plant roots. Nevertheless, the temperature alteration ratio below 40 °C of substrate with plant root is nearly the same as its counterpart in the substrate without roots. The resistance of the substrate with plant roots increases with the temperature. The resistance of rootless substrate decreases by the heat action of the loosely bound water. EPS particles improve the heat preservation performance of substrate, but the heat preservation performance of substrate degrades with the growth of plants.

Measurement of temperature-dependent thermal conductivity for PVD Ti0.55Al0.45N ceramic coating by time domain thermo-reflectance method

Accurate measuring temperature-dependent thermal conductivities of (Ti,Al)N ceramic coating is important to quantitatively analyze the thermal effects of (Ti,Al)N ceramic coating on the heat generation and heat transfer during cutting process by PVD (Ti,Al)N coated cemented tools. In this paper, the temperature-dependent thermal conductivities of PVD Ti0.55Al0.45N ceramic coating with coating thickness of 2 µm in the temperature ranges of 25–500 °C are measured by time domain thermo-reflectance method. Firstly, the detailed deposition process and microstructure characterization of PVD Ti0.55Al0.45N ceramic coating are presented. Secondly, the measuring principle and measuring procedure of PVD ceramic coating thermal conductivity with the time domain thermo-reflectance are proposed. Then, the measured thermal properties of substrate are used in the calculation algorithm to obtain the thermal conductivity of Ti0.55Al0.45N ceramic coating at the specific temperature, which can eliminate the variation influences of substrate thermal properties with temperature. Lastly, the obtained thermal conductivities of PVD Ti0.55Al0.45N ceramic coating are verified to be increased with the increase of temperature in the temperature ranges of 25–500 °C. The relationship between the thermal conductivity of PVD Ti0.55Al0.45N coating and temperature can be represented by quadratic polynominal equation. The applied time domain thermo-reflectance method is useful for measuring the temperature-dependent thermal conductivities of similar ceramic coatings in the temperature ranges of 25–500 °C.

High Pressure Cryogenic Nitrogen Jet for Clean Coating Removal: Experimental Study of Polyamide Ablation

The potential of a recently developed technique that uses a clean supercritical High Pressure Cryogenic Nitrogen Jet (HPCryoN2Jet) for surface ablation and cleaning is depicted. In contrast to existent coating-removal techniques (chemical stripping, hydro-blast, water jet cleaning...), as nitrogen is naturally recycled in the air, this process has a high potential for surface treatment without any chemical and physical effluents or sewage disposal. The treatment consists in impacting the surface with a high pressure (up to 3500 bar) cryogenic nitrogen jet (down to-160°C). The pressurized cryogenic nitrogen exits from a nozzle - having generally a 0.2 to 0.5 mm diameter outlet - to form the high velocity (supersonic) nitrogen jet. In this contribution, the ability of the process to remove polymeric (PA) coatings is evaluated on different types of metallic substrates (Cu, Al, E24, 316L stainless steel). The mechanisms of chip formation have been visualized using a high speed camera. Coating failure is shown experimentally to occur downstream of the jet and the influence of the substrate thermal properties on the stripping efficiency of the PA coating is highlighted.

Optimizing the substrate-mediated laser ablation of biological tissues: Quest for the best substrate material

Laser micro-sampling is a promising tool for ambient pressure chemical imaging of biological material by mass spectrometry. Conventional approaches use laser energy coupling into the analyzed sample through electronic (UV) or vibrational (IR) channels. In a recent study [B. Fatou, M. Wisztorski, C. Focsa, M. Salzet, M. Ziskind, I. Fournier, Sci. Rep. 5:18135, 2015], we have demonstrated efficient micro-sampling of biological material through a substrate-mediate laser ablation (SMLA) mechanism using non-resonant visible radiation. Taking advantage of this effect, a large-scale proteomic analysis of micro-sampled tissue sections was performed, demonstrating the possible identification of about 400 proteins, including minor species, from an irradiated surface of 400 μm diameter. Fundamental investigations on biological standards revealed the role of the substrate optical properties in the ejection process. In the present work, we extend these studies by considering the substrate thermal properties. A systematic investigation on the sampling efficiency of homogeneous tissue sections placed on top of various selected substrates was performed. Two ejection mechanisms are clearly evidenced and interpreted in the frame of a simple model based on the substrate properties and the laser beam profile. Improvement of the ejection yield and spatial resolution is also discussed in this frame, in view of the practical application of this technique in the field of (bio)chemical mass spectrometry imaging.