Thermal Controllability Research Articles

The preparation and feasibility analysis of magnetic orientation method in the study of thermal insulation composite materials in the field of electronic packaging

AbstractAs an emerging field of current technological development, the heat dissipation performance of electronic packaging materials has become the key to determining product reliability. Therefore, the applied thermal interface materials (TIMs) need to simultaneously meet the performance indicators of thermal conductivity, mechanics, and insulation. Although BN had excellent in‐plane thermal conductivity and insulation performance, it is currently difficult to achieve vertical orientation of powder which leads the layered powder cannot complete a continuous and effective heat transfer path along the Z‐axis direction inside the composite material. In order to solve the above two problems, out‐of‐plane thermal conductive composite was prepared by introducing magnetic oriented method. In order to comprehensively evaluate the thermal conductivity, mechanical and electrical properties, BN@Fe3O4/EP magnetic oriented composites were compared with BN@PDA‐Al2O3/EP composite prepared by mechanical blending method. The vertical thermal conductivity of the magnetic oriented composite material was 2.24 W/(m·K) at 30 vol%, which was 3.39 times that of the blended composite material and 12.4 times that of pure EP. This proves that the magnetic oriented composite materials prepared by the research institute can meet the vertical heat transfer needs in the field of electronic packaging and have high research value in this area.Highlights BN@Fe3O4 core–shell particles were prepared with both thermal conductivity and magnetic controllability. The thermosetting composites were prepared by heated through preliminary gel point and then cured at high temperature. The orientation of powder inside the matrix was constructed, resulted in excellent out‐of‐plane heat transfer performance. Comparisons were made between various properties of magnetic oriented materials and conventional blend materials. The magnetic orientation method is feasible in the field of electronic packaging.

Thermal safety and overall kinetics for methyl methacrylate solution polymerization via on-line process analytical technology

Polymethyl methacrylate (PMMA) is widely used, but its polymerization process is highly hazardous and the relevant thermal hazards have not been adequately investigated. Herein, the thermal safety and kinetic mechanisms of methyl methacrylate (MMA) polymerization are explored. The effect of monomer concentration on the exothermic characteristics is first investigated using a reaction calorimeter. The results indicate that the exothermic behavior of this reaction is significantly influenced by the monomer concentration. Meanwhile, a quantitative relationship between the specific enthalpy and monomer concentration is determined. Moreover, overall rate expression is developed by a rapid quantitative method to further elucidate the quantitative dependence of reaction rate on the process conditions. Subsequently, adiabatic experiment is performed to reveal the thermal controllability of this reaction. Finally, risk level is ascertained to propose constructive countermeasures. This work provides guidance for the safe operation of MMA polymerization, and the methodology also furnishes universal solutions for analogous reactions.

Curing and self-healing of enzymatic construction materials using nanoparticles

Preparation of construction materials on site may offer advantages in transportation and storage. However, a major limitation of on-site preparation of some materials is the need for heat and oven desiccation for adequate curing. Here, we describe a method that allows rapid curing under ambient conditions through the addition of 0.1% iron oxide nanoparticles to a carbon-negative enzymatic construction material (ECM) to make ECM-n. Specifically, we show that a low-power laser (3W at 808 nm) can cure ECM-n to an optimal mechanical strength in 12 h, which can be compared to the 14-day period needed for in situ air drying. In addition, the incorporation of nanoparticles allows rapid self-healing of large-scale flaws and that incandescent light can be used if lasers are not available. This method establishes an on-site manufacturing capability for ECM-n and other construction materials and supports thermal controllability of the local structure in low-temperature regions. • Introduction of curing method that allows for on-site fabrication • Nanoparticles reduce the curing period in a recently developed ECM-n • Curing can be carried out using a low-power laser or other light sources • ECM-n can be used as a multifunctional thermal element Wang et al. report the application of nanoparticle methodology where particles are added to enzymatic construction material (ECM) to allow curing at ambient temperatures without the need for heat/desiccation for on-site fabrication. In addition, the material can be rapidly repaired when built-in flaws are introduced.

Dynamically Selective and Simultaneous Detection of Spin and Orbital Angular Momenta of Light with Thermoresponsive Self-Assembled Chiral Superstructures

Featuring a self-assembled helical nanostructure and external stimuli-responsive chiral photonic band gap, cholesteric liquid crystals (CLCs) create more opportunities in harnessing multiple degrees of freedom of light, especially the spin and orbital angular momenta (SAM/OAM). Here, we propose and demonstrate an innovative method for a dynamically selective and simultaneous detection of SAM and OAM of light via two cascaded CLC superstructures with thermal controllability and opposite chirality. By independently regulating their temperatures, on-demand selective detection for the intended wavelength and spin eigenstate is achieved with high efficiency and broadband tunability. The information of the desired angular momenta is vividly identified by the reflected diffraction patterns from cascaded chiral superstructures, while the nondetected components are preserved in the transmitted light. This indicates an in situ and nondestructive manner and may facilitate advanced optical manipulation, imaging, and information (de)multiplexing. This work brings important insights into the design, construction, and application of self-assembled chiral nanostructures, promoting multiple and active functionalities in diverse intelligent devices.

Phase change materials for waste heat recovery in internal combustion engines: A review

Since most of the energy consumed by an internal combustion engine (ICE) is wasted, heat recovery from the exhaust and coolant is considered as a promising technology for improving the engine efficiency. The systems that used for recovering wasted thermal energy are called waste heat recovery (WHR) systems. However, most WHR methods suffer from main drawbacks such as difficult implementation, low thermal controllability and poor thermal storability. These drawbacks could be overcome by integrating thermal energy storage (TES) systems with ICEs. TES relies on sensible heat, latent heat and thermochemical storage. Latent heat storage method with phase change materials (PCMs) is the most utilized in ICEs because of its good controllability and high storage capacity. Therefore, this review presents the applications of TES with PCMs for recovering waste energy in ICEs. The literature shows that PCMs could be incorporated into different ICEs systems including exhaust recovery systems, cooling recovery systems, catalytic converters, diesel generators, evaporator and pressure regulators, additional diesel heaters, and cylinder's body. The previous studies on these systems show the potential of TES with PCMs in storing and recovering waste heat. Moreover, it is shown that the recovered heat by PCMs is mainly used for purposes of engine pre-heating during cold-start, maintaining hot temperature of catalysts for better conversion efficiency, and heating domestic and industrial water. Finally, the problems of PCMs with ICEs such as bulky system problem, high initial cost, corrosion issues, and poor stability; are also discussed in this review.

Controlling the thermal conductivity of multilayer graphene by strain

Straintronics is a new concept to enhance electronic device performances by strain for next-generation information sensors and energy-saving technologies. The lattice deformation in graphene can modulate the thermal conductivity because phonons are the main heat carriers. However, the device fabrication process affects graphene’s heat transport properties due to its high stretchability. This study experimentally investigates the change in the thermal conductivity when biaxial tensile strain is applied to graphene. To eliminate non-strain factors, two mechanisms are considered: pressure-induced and electrostatic attraction–induced strain. Raman spectroscopy and atomic force microscopy precisely estimate the strain. The thermal conductivity of graphene decreases by approximately 70% with a strain of only 0.1%. Such thermal conductivity controllability paves the way for applying graphene as high-efficiency thermal switches and diodes in future thermal management devices.

Tunable Bandpass Filter With Serially Coupled Ring Resonators Assisted MZI

We present the analytical modelling and experimental characterization of a new design of silicon nitride tunable bandpass filter based on serially coupled ring resonators assisted Mach-Zehnder interferometer (SR-MZI). SR-MZI filters provide an additional degree of freedom to independently control the bandwidth and shape of the passband as compared to previous ring-assisted MZI filters. It is possible to tune the bandwidth, shape and side-band rejection of the response by adjusting the coupling in the filters, providing a scope for fully reconfigurable performance. The fabrication of the filters is CMOS compatible and supports mass production. Preliminary results for thermal controllability are presented.

Conjugated Organic Photothermal Films for Spatiotemporal Thermal Engineering.

With the growth of photoenergy harvesting and thermal engineering, photothermal materials (PTMs) have attracted substantial interest due to their unique functions such as localized heat generation, spatiotemporal thermal controllability, invisibility, and light harvesting capabilities. In particular, π-conjugated organic PTMs show advantages over inorganic or metallic PTMs in thin film applications due to their large light absorptivity, ease of synthesis and tunability of molecular structures for realizing high NIR absorption, flexibility, and solution processability. This review is intended to provide an overview of organic PTMs, including both molecular and polymeric PTMs. A description of the photothermal (PT) effect and conversion efficiency (ηPT ) for organic films is provided. After that, the chemical structure and optical properties of organic PTMs are discussed. Finally, emerging applications of organic PT films from the perspective of spatiotemporal thermal engineering principles are illustrated.

A chemical micropump actuated by self-oscillating polymer gel

Abstract We demonstrated a self-driven chemical micropump powered by self-oscillating motions of synthetic polymer gel converting chemical energy into displacements of a thin polydimethylsiloxane (PDMS) sheet to produce a directional flow via micro check valves. The gel oscillations induced by the oscillatory Belousov-Zhabotinsky (BZ) reaction generate large volume change. To effectively exploit this volume change, gel bars were used as drivers. They were sandwiched by a fixed cover glass and a push-bar to communicate the expanding (pushing) force of the gel bars to the pumping chamber. At 25 °C, this gel micropump generated a 0.07 mN stroke force and a 0.28 μL/min positive net flow in the microchannel. Additionally, the flow rate of this gel micropump was increased as the temperature was raised from 20 to 30 °C. Compared to existing chemical micropumps, this gel-based micropump provides advantages of self-oscillating property, easy refueling and thermal controllability. This gel-based soft micropump would be used as wearable or medical devices exploiting the flexibility and quietness.

A comparative study on the applicability of six radiant floor, wall, and ceiling heating systems based on thermal performance analysis

Holistic comparisons of radiant heating systems that would help make an informed decision on the selection of the most convenient system for the specific application are lacking. The applicability of six representative radiant floor, wall, and ceiling heating systems was therefore compared in terms of thermal output and surface area required, controllability, short-term and long-term heat storage, suitability for building retrofit, and investments. Temperature and heat flux distribution in the structure, time constant τ63, response time τ90, and the number of operating cycles were computed by a custom-made and verified software tool using the finite volume method. Thermal energy stored was used to determine the ability of energy storage, whereas investment costs indicated affordability. Wall heating with pipes attached to a thermally insulating core had the highest thermal output, was easy to control, suitable for building retrofit, and most affordable while providing limited thermal storage. The performance of the wall system was retained when locating the pipes in plasterboard separated from the core by an air gap. Floor heating performed consistently in all the aspects evaluated. It was demonstrated that inserting a metal fin between pipes and the concrete spread layer improved thermal output, controllability, and storage capacity of the floor system with minor effect on investments. Ceiling with pipes insulated from the core performed well when thermal storage was not required. Ceiling with pipes embedded in the core was only feasible when long-term heat storage was needed.

CFD modeling of a compact reactor for methanol synthesis: Maximizing productivity with increased thermal controllability

A kinetic model for methanol synthesis was validated for a conventional fixed-bed reactor at the mini-pilot scale by determining a heat transfer coefficient to fit the experimental data satisfactorily. To enhance the thermal controllability of the reaction system, a compact reactor, which utilizes heat transfer with both cooling media and cool feed gas, was introduced. The analysis of detailed profiles of mass, momentum, and heat was conducted by applying the developed kinetic model to the computational fluid dynamics modeling approach. While the accumulation of heat was observed in a conventional reactor because of its limited heat transfer capability, a compact reactor could efficiently remove the generated heat. The space velocity and feed temperature were manipulated to increase the production rate while unstable thermal behavior was prevented, and it was clearly shown that the proposed reactor could produce twice the methanol, with its peak temperature maintained below the conventional one. When the diameter of the catalytic bed in the compact reactor was increased, the reaction remained in the kinetic regime, resulting in high methanol productivity as well as maximum utilization of the bed.

Thermal conductivity enhancement of form-stable tetradecanol/expanded perlite composite phase change materials by adding Cu powder and carbon fiber for thermal energy storage

In this study, form-stable tetradecanol (TD)/expanded perlite (EP) composites by adding Cu powder (CuP) and carbon fiber (CF) to enhance thermal conductivities have been prepared via vacuum impregnation method. The thermal conductivity enhancer (TCE) is introduced by two methods of mixing TCE with phase change materials (PCMs) and implanting TCE into matrix materials. The result demonstrates the former is better than the latter in aspects of thermal property, thermal conductivity and controllability, moreover, adding ratio of TCEs gather in more appropriate interval from 2.5% to 3% suitable for the former. For CPCMs, FT-IR results indicate it is no chemical interaction among raw materials but physical combination via two methods. CPCMs prepared by the method of mixing TCE with PCMs have better phase change latent heat and thermal stability by DSC and TGA, while thermal cycling measurements show that form-stable composite PCMs have adequate stability even after being subjected to 200 melting/freezing cycles. Therefore, the method of mixing TCE with PCMs has better thermal property and controllability than that of implanting TCE into matrix materials and the prepared CPCM has great application prospect in solar energy utilization, building material, indoor cooling instrument and so on for thermal energy storage.

Novel thermal controllability and designability of thermal transport at the nanoscale

Novel thermal controllability and designability of thermal transport at the nanoscale

Thermal diode using controlled capillary in heterogeneous nanopores

The development of a compact, efficient, reliable thermal diode is crucial to improve advanced thermal management efficiency and controllability, and to enable brand new applications such as thermal logic gates and computers. In this study, we examine a nanoscale and efficient capillary-controlled thermal diode mechanism in Ar-filled Pt-based heterogeneous nanoporous structures, using Grand Canonical Monte Carlo (GCMC) simulation combined with Non-Equilibrium Molecular Dynamics (NEMD) simulation at the temperature range of 70–150 K and the pressure of 1.66 atm. Results show that the large thermal conductivity contrast between the controlled adsorption and capillary states using the structural heterogeneity (nanopillars on only one surface) and/or material heterogeneity (two different materials for nanogap surfaces) allows for the maximum thermal rectification ratio, Rmax ∼ 140 with minimal hysteresis under the cyclic operating temperatures −40 K < ΔT < +40 K. It is also found that the material heterogeneity is equivalent to the structural heterogeneity for minimizing the hysteresis in adsorption-capillary transition, but the heat flux across the nanogap with the material heterogeneity reduces due to weaker Ar-solid interaction. The coupled structural-material heterogeneity for the capillary-driven thermal diode is also discussed. The obtained results pave pathways for advanced thermal management systems such as thermal transistors, thermal logic gates, and computers.

Comparison of Single- and Twin-Shaft CCPPS

The main advantages and disadvantages of single- and twin-shaft CCPPs are analyzed, taking into account various configurations and thermal efficiency and controllability. Single-shaft configurations with and without freewheeling clutch between the electric generator and the steam turbine are considered. Single-shaft 370 – 420 MW CCPPs operated in Russia are compared with twin-shaft units of the same capacity.

Transparent Perovskite Barium Stannate with High Electron Mobility and Thermal Stability

Transparent conducting oxides (TCOs) and transparent oxide semiconductors (TOSs) have become necessary materials for a variety of applications in the information and energy technologies, ranging from transparent electrodes to active electronics components. Perovskite barium stannate (BaSnO3), a new TCO or TOS system, is a potential platform for realizing optoelectronic devices and observing novel electronic quantum states due to its high electron mobility, excellent thermal stability, high transparency, structural versatility, and flexible doping controllability. This article reviews recent progress in the doped BaSnO3 system, discussing the wide range of physical properties, electron-scattering mechanism, and demonstration of key semiconducting devices such as pn diodes and field-effect transistors. Moreover, we discuss the pathways to achieving two-dimensional electron gases at the interface between BaSnO3 and other perovskite oxides and describe remaining challenges for observing novel quantum phenomena at the heterointerface.

Polarization controllable multispectral symmetry-breaking absorberin mid-infrared

The versatility of mid-infrared metamaterial absorbers along with the ease of fabrication has been widely used in thermal imaging, molecule sensing, and many other applications. Controllable multispectral absorption is highly required for small footprint, multi-purpose, and real-time sensing applications. In this paper, we present the polarization control of interchangeable multispectral absorption based on the dual-band metamaterial absorber in split mode. Large modulation depth of absorption is obtained during multi-band transition through polarization control. We perform theoretical and numerical analysis to explain the results by formulating an equivalent circuit for the asymmetric cross resonator. Thermal controllability is also demonstrated to show the reversible and repeatable manipulation of absorption intensity at a given wavelength. Moreover, we characterized the limitation of this device under extreme high temperature. This work offers a design methodology for interchangeable multispectral metamaterial absorber from a new perspective by adopting polarization of incident light as a control mechanism, and this will open up possibilities for many valuable applications in the future.

Thermal behavior of wafers and its effects on overlay performance in immersion lithography

In semiconductor manufacturing below 45nm node, immersion lithography is serious technique to increase depth of focus (DOF) at obtainable apertures and to improve resolution with apertures higher than one. However, immersion environment between wafer and lens could be responsible for a net reduction in overlay performance due to wafer temperature instability during exposure. In this paper, we have investigated correlation of thermal behavior of wafer during exposure and overlay performance. It was founded that the thermal effect of concentric distribution on wafer scaling (correctable errors) is lager (0.1ppm) than uniform distribution. In grid and field residual analysis, the grid residual errors was demonstrated a good correlation (R^2=0.92) with thermal variation. However, there was little relationship (R^2=0.3) between the field residual errors and thermal stability. These results indicated that progressed thermal controllability for both spatial and temporal variation can be converted into improved overlay accuracy in immersion lithography.

Crystallization of 640 kg mc-silicon ingots under traveling magnetic field by using a heater-magnet module

For the first time a heater-magnet module (HMM), simultaneously generating heat and a traveling magnetic field (TMF), was constructed for an industrial scale G5 multi-crystalline Si crystallizer and extensively tested. Effective melt mixing and precise control of the interface shape have been demonstrated using TMF, which resulted in ingots exhibiting superior properties, clearly proving the beneficial effects of the advanced convection control without affecting the stability of the Si3N4 crucible coating. Hence, most of the solidified Si volume showed very homogeneous IR transmission without inclusions. Dislocation densities were relatively low and bunching was only rarely observed, resulting in overall high carrier lifetimes. Therefore, our results demonstrate that a HMM configuration in an industrial Si crystallizer may successfully accomplish the following tasks: (i) good thermal stability and controllability of the melt-solid interface morphology, (ii) suppression of second phase inclusions, such as SiC and Si3N4, by mastering the mixing of the melt during the whole crystallization process, and (iii) no pronounced interaction between melt and container wall.

Tunable terahertz-mirror and multi-channel terahertz-filter based on one-dimensional photonic crystals containing semiconductors

We demonstrate that tunable terahertz-mirrors and multichannel terahertz-filters can be carried out by taking into account the transmission properties of the one-dimensional photonic crystals (1DPCs) containing semiconductor materials with a tunable dielectric constant in the THz frequency range. Using the semiconductor InSb as the components in the 1DPCs, we have designed such a mirror and a filter and identified their tunability. The THz-mirror is tunable by changing the external temperature or the thickness of the components of the 1DPC. The operation frequency of the multichannel-filter can be tuned by changing the temperature and thickness of the component materials in the 1DPC, the channel number of the filter can be controlled by varying the number of the defect layers in the 1DPC, and the transmittance bandwidth can be adjusted by changing the period number of the 1DPC. With thermal tunability, structure controllability and narrow bandwidth, 1DPCs containing semiconductors open a promising way to fabricate tunable terahertz devices for future terahertz communications.