Insulation Barrier Research Articles

English

In this contribution, we present the problem of shape optimization of the plunger cooling which comes from the forming process in the glass industry. We look for a shape of the inner surface of the insulation barrier located in the plunger cavity so as to achieve a constant predetermined temperature on the outward surface of the plunger. A rotationally symmetric system, composed of the mould, the glass piece, the plunger, the insulation barrier and the plunger cavity, is considered. The state problem is given as a multiphysics problem where solidifying molten glass is cooled from the inside by water flowing through the plunger cavity and from the outside by the environment surrounding the mould. The cost functional is defined as the squared $$L^2_r$$ norm of the difference between a prescribed constant and the temperature on the outward boundary of the plunger. The temperature distribution is controlled by changing the insulation barrier wall thickness. The numerical results of the optimization to the required target temperature 800 ◦C of the outward plunger surface together with the distribution of temperatures along the interface between the plunger and the glass piece before, during and after the optimization process are presented.

Microstructure and peeling behavior of MOCVD processed oxide insulator coating before and after ion beam irradiation

The mechanical durability and soundness of the several oxide coating materials used as the electrical insulator and tritium permeation barrier are important design parameters on an advanced liquid breeding blanket system. We tried to investigate the adhesion strength evaluation due to the peeling behavior on the MOCVD processed multilayered oxide coating (Er2O3/Y2O3) on the stainless steel (SUS) substrate before and after Cu2+ ion beam irradiation using the nano-scratch tester. The adhesion strength of the coating material was able to estimate easily from the scratch trace and scratch stress, and the nano-scratch test was suitable method to evaluate the mechanical durability and soundness. After the Cu2+ ion beam irradiation, the adhesion strength was decreased with increasing the displacement per atom (dpa). The adhesion strength degradation by the Cu2+ ion beam irradiation was caused by the embrittlement of the thicker and amorphous Fe-(Y)-O interlayer formation between Y2O3 buffer layer and SUS substrate based on the displacement damage dose effect.

Physical property changes of neutron-irradiated aluminum nitride and their recovery behavior by annealing using a step-heating dilatometer

Aluminum nitride (AlN) is a candidate tritium permeation, electric insulation and corrosion barriers for several kinds of blankets such as molten salt–cooled (FLiBe) or liquid metal (Li-Pb or Li)-cooled blankets because of its desirably low dielectric constant and tritium diffusion. Commercially available AlN ceramic specimens were neutron-irradiated at two different fluences but the same irradiation temperature in the Japan Materials Testing Reactor. Specimen swelling was found to be slightly different for both conditions, with higher dose causing greater swelling. All irradiated specimens consisted from hexagonal AlN phase with α-Al2O3 phase occurring on the surface after long-time post-irradiation annealing in He atmosphere. The a- and c-axis experienced isotropic increase and degree of unit-cell volume change was almost the same with the macroscopic volume increase obtained from the length change. This result indicates uniform distribution of Frankel pairs. After step-wise thermal annealing by using a dilatometer up to 1673 K for 6 h at each step, the maximum recovery was found at 1573 K. Based on the recovery rates at each step by first-order analysis, macroscopic length recovery during annealing can be divided into three regions with different activation energies, low temperature (373–523 K) with ∼4.5 eV, intermediate temperature (523–873 K) with 0.5–1.0 eV, and high temperature (873–1273 K) with 2.0–2.5 eV. Over 1273 K, a slight increase of length was observed. It is thought that the expansion is due to oxidation.

(Invited) Two-Dimensional Wide Bandgap Materials for Electronic Applications

The emerging two-dimensional (2D) materials, such as graphene, MoS2, and hexagonal boron nitride (hBN), are promising candidates for next-generation electronics. Gapless graphene has intriguing properties of ultrahigh mobility, transparency, tunable charge neutral point, etc. Differently from conventional semiconductors, 2D semiconductors, representatively transition metal dichalcogenides (TMDs), have shown unprecedented characteristics, such as indirect-to-direct band transition, trions, and valleys, which can be utilized to realize new-function devices. Despite rigorous researches on these 2D materials, wide bandgap 2D materials have not been studied widely and actively due to limited material sources. However, it should be noted that these wide bandgap 2D materials are essential for practical applications of 2D-material-based electronics because these insulating blocks are required to form multi-stacked 2D devices. Here I present electrical/optical characteristics of wide bandgap 2D materials, such as hBN and MoO3, and electronic devices consisting of van der Waals heterostructures of the 2D materials. 2D insulators with large bandgap were used as atomically thin insulator or tunnel barrier for ultrathin devices. It was also confirmed that 2D oxide layers can be epitaxially grown on 2D substrates of graphene and hBN. Growth of highly crystalline 2D oxide layers on other 2D layers shows great potential for large scale production of 2D oxides, which are highly useful for future electronics. Our approaches would allow us to come closer to practical applications of 2D materials in industry.

Enhanced Thermal Resistance and Electrochemical Performance of the Trilayered PP/PE/PP Separators Using Alumina Coating for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have served as a potential power source for portable electric vehicles and energy storage devices due to their high energy capability, high power density, cost competitiveness, long cycle life and little memory effect. However, safety issue is still one of the most challenges in affecting widespread use of LIBs as power sources. As a key component of LIBs, the separator should maintain electronic insulation between cathode and anode, enabling free ionic transport and isolating electronic flow. To reach the demand of safety issue, the design of separator takes one task that is responsible for preventing an internal short circuit from thermal evolution. An ideal separator is therefore expected to possess high ionic conductivity, excellent thermal stability, and superior electrochemical performance. One strategy to improve the thermal stability and electrolyte wettability on the separators is introducing ceramic coating layers containing hydrophilic inorganic powders such as ZrO2, SiO2, TiO2, and Al2O3. The above achievements direct us at the development of facile methods to improve the polymeric separators to meet the requirements of high-performance LIBs. Recently, polymeric membranes such as the tri-layered PP/PE/PP have been extensively used as separators for LIB applications. This work work adopts a chemical-wet impregnation method to prepare alumina-coated separator, using commercial Al2O3 nanoparticles and poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) binder. The PVdF-HFP binder contains a ternary mixture comprising the polymer (PVdF-HFP), solvent (acetone), and nonsolvent (water), which is appropriate to mix with ceramic nanoparticles. One potential electrode material, spinel Li4Ti5O12, is served as the anode for the analysis of electrochemical performance, using charge-discharge cycling and electrochemical impedance spectroscopy. Three densities of Al2O3 nanoparticles are uniformly dispersed and coated onto the surface of tri-layered polymeric separators. The bare and Al2O3-coated separators were denoted to U, AS1, AS2, and AS3 according to the weight ratio of Al2O3 to PVdF-HFP solution of 0, 0.06, 0.12, and 0.25 wt.%, respectively. TGA curves reflect that the thermal resistance of tri-layered separators is significantly enhanced after the deposition of Al2O3 coating layers. The alumina deposits display high thermal resistive ability under O2-containing atmosphere. Moreover, FE-SEM images show that the alumina nanoparticles with an average particle size of 300 nm are uniformly dispersed on the surface of the separators. With increasing alumina loading, close-packed Al2O3 nanoparticles interconnected by PVdF-HFP binder are grouped and coated upon the surface of the separators. Typical XRD patterns reveal that bare separator (U) possesses its original reflection bands, while alumina-coated separators (AS1, AS2, and AS3) exhibit additional representative bends, confirming the presence of α-Al2O3 crystals. On the other hand, the mass uptake of the electrolyte (1.0 M LiPF6 in a mixture of ethylene carbonate, propylene carbonate, and dimethyl carbonate with a weight ratio of 1:1:1) on the bare separator (U) is 270 mg cm-2, whereas that on AS1 separator attains as high as 515 mg cm-2. Also, the mass uptake on AS3 separator is 2.2 times higher than that of the bare one. The extent of thermal shrinkage on AS3 sample is ~2.26 times higher than that on U sample. This confirms that an obvious enhancement on thermal stability of polymeric polymer can achieve after the introduction of alumina coating, also demonstrated by the TGA results. With regard to electrochemical performance, the LIB using AS3 separator delivers the highest discharge capacity among these samples, i.e., 166 mAh g-1 (0.1C) and 160 mAh g-1 (1C). The enhanced rate capability is presumably due to high Li-ion storage capacity and excellent wettability, imparting low Li-ion diffusion resistance and then speeding up electronic conduction. With the aid of Al2O3 coating layer, the equivalent series resistance of electrode is significantly reduced and the ionic conductivity is strongly improved, according to analysis of ac impedance spectroscopy. In a word, the amount of Al2O3 nanoparticles is picked up as a key parameter in examining electrochemical performance and thermal stability of LIBs. The enhanced performance is ascribed to the fact that Al2O3 coating layer is served as a robust skeleton to stabilize the separators, imparting a superior insulation and mass transport barrier against volatile compounds formed during the thermal decomposition process.

Evaluation of the thermal performance of insulation sheets in fiberglass security booths

In light-weight buildings under subtropical climatic conditions, it is recommended the use of roof materials that minimize heat gains in summer while avoiding heat losses in winter. A low-cost option for ensuring thermal insulation with radiant barriers and reflective elements is based on the use of open Tetra Pak® packages. The aim of the study was to evaluate the thermal performance of three kinds of insulation strategies, resistive insulation, reflective insulation and radiant barriers: 50 mm Expanded Polystyrene (EPS), double-sided foil insulation and Tetra Pak® sheets, used under the roof of fiberglass security booths. Comparisons of indoor air and surface temperatures were carried out during transitional periods: spring-summer and fall-winter. Tetra Pak® sheets with an upward-facing (acting as reflective insulation) or downward-facing (functioning as radiant barrier) aluminized side or with double-sided aluminum coating showed a reduction in the roof's inner surface temperature, comparable to commercial insulating sheets, though with lesser effect on indoor temperatures. For the spring-summer transitional period, results for double-coated Tetra Pak® sheets were superior to those of commercially available double-sided foil insulation.

Multi-layer embedded carbon fibres as highly compliant and stretchable interconnects

This paper describes a unique technique to manufacture highly stretchable and implantable interconnects. A possible application is presented, where the interconnects are intended to create a network of nodes sensing biological parameters in e.g. the bladder wall. The interconnects are fabricated by embedding nickel-plated carbon fibres bundles first in a thin polyurethane tube and then in a soft, elastic, polydimethylsiloxane matrix. The insulation barrier properties of the proposed packaging technique were verified by a leakage current measurement performed in body mimicking media. The use of multiple thin fibres increases the amount of bending cycles before mechanical failure occurs. Carbon fibres possess extraordinary fatigue resistance and can withstand more than 160 000 deformation cycles under normal operating conditions without failing and display minimal impedance change. Patterning the polymeric matrix in a meander shape, along with the conductors, allowed the fabrication of extremely compliant interconnects that can achieve large deformations in response to low tensile stress. Due to the carbon fibres’ strength, the only factor limiting the device’s ultimate elongation is the geometrical length of the meandering structure itself. Even when stretched to its maximum, beyond normal operating conditions, the completely assembled device survived 20 000 loading cycles before failure of the polymeric coating. The proposed interconnects can follow the extensive deformation of the biological structures they are attached to, and can be stretched to 200% of their original length with less than 0.1 N of applied force.

Assessment of Energy Barriers Between ZrCuAlNi Amorphous Metal and Atomic Layer Deposition Insulators Using Internal Photoemission Spectroscopy

The energy barrier heights between an ultra‐smooth amorphous metal electrode, ZrCuAlNi, and several atomic layer deposited (ALD) insulators are measured using internal photoemission (IPE) spectroscopy. ZrCuAlNi–insulator barriers are characterized within metal–insulator–metal (MIM) stacks with Al top contacts and results are compared with the Al/insulator barrier heights. The measured barrier heights at the ZrCuAlNi interface are found to be 3.3, 3.2, 3.0, and 2.2 eV for SiO2, Al2O3, HfO2, and ZrO2, respectively. This barrier height trend is consistent with the electron affinity of the respective oxides. However, barriers for SiO2 and Al2O3 are smaller than that ideally expected based on the reported vacuum work function of ZrCuAlNi, indicating a smaller ZrCuAlNi effective work function in these device structures. The measured Al barrier height results confirm previous reports of a negative dipole at the Al–ALD insulator interface.

Synthesis of TPU/TiO2 nanocomposites by molten blending method

Efficient flame-retardant TPU/TiO2 nanocomposites were synthesized by molten blending method. The morphological and structural analysis indicated that TiO2 nanoparticles could be well dispersed in TPU and increased compatibility with the polymer. The obtained mechanical and thermal data suggested that intense cross-linking interaction between TiO2 and TPU promoted more stable network structure, which increased tensile length at break, storage modulus and loss modulus and thermal stability. Furthermore, the cone results demonstrated that TiO2 could not only decrease HRR, but also provide more stable char due to its high heat resistance, and catching and isolating oxygen molecules. Though ignition was inevitably earlier and peak value appearance caused transient thermal conductivity, TiO2 could greatly deplete combustible smoke particulates on the surface of TPU by accelerating degradation of combustible gases to prevent further penetration and destruction from TPU surface as oxygen insulation barrier. Therefore, TiO2 as a kind of effective flame-retardant and smoke suppression material can be applied in the flame retardancy of TPU.

Electrical transport across nanometric SrTiO3 and BaTiO3 barriers in conducting/insulator/conducting junctions

We report the electrical transport properties of conducting/insulator/conducting heterostructures by studying current–voltage IV curves at room temperature. The measurements were obtained on tunnel junctions with different areas (900, 400 and 100 μm2) using a conducting atomic force microscope. Trilayers with GdBa2Cu3O7 (GBCO) as the bottom electrode, SrTiO3 or BaTiO3 (thicknesses between 1.6 and 4 nm) as the insulator barrier, and GBCO or Nb as the top electrode were grown by DC sputtering on (100) SrTiO3 substrates For SrTiO3 and BaTiO3 barriers, asymmetric IV curves at positive and negative polarization can be obtained using electrodes with different work function. In addition, hysteretic IV curves are obtained for BaTiO3 barriers, which can be ascribed to a combined effect of the FE reversal switching polarization and an oxygen vacancy migration. For GBCO/BaTiO3/GBCO heterostructures, the IV curves correspond to that expected for asymmetric interfaces, which indicates that the disorder affects differently the properties at the bottom and top interfaces. Our results show the role of the interface disorder on the electrical transport of conducting/insulator/conduction heterostructures, which is relevant for different applications, going from resistive switching memories (at room temperature) to Josephson junctions (at low temperatures).

Oil Impregnated Pressboard Barrier Systems Based on Ester Fluids for an Application in HVDC Insulation Systems

Ester-based insulation fluids are being increasingly used in high-voltage insulation systems. The reasons are the advantages in the area of ecological compatibility and resource-saving provision. The intention to use ester-based insulation fluids in high voltage direct current (HVDC) equipment is new. The major challenge in designing the HVDC insulation system is, that the systems do not only experience an alternating voltage, but also a direct voltage Offset. This presents a challenge to predict the electric field distribution. For this purpose, basic investigations are carried out in the form of conductivity investigations for various insulation barrier systems. In addition, a mineral oil serves as a reference oil for estimating existing insights. The results show the influence of the ester-based insulating liquids on the direct current (DC) conductivity for basic arrangements, consisting of pressboard barriers and mixed insulations.

Sol–gel deposition of silica nanospheres onto polymeric separators for improved performance of Li-ion batteries

Abstract This work presents an efficient sol–gel method to coat SiO 2 nanopheres onto tri-layered polymeric separators for Li-ion batteries, consisting of Li 4 Ti 5 O 12 (LTO) anode/Li cathode. The surface density of silica nanospheres with diameter of 300–500 nm is chosen as controlling factor in affecting the electrochemical performance and thermal stability of Li-ion batteries. The SiO 2 deposition on the polymeric separators exhibits not only an enhanced thermal and dimensional stability but also an improved rate capability and inner resistance. The excellent performance originates from the formation of robust skeleton to stabilize the separators, allowing a superior insulation and mass transport barrier against volatile compounds generated during thermal decomposition process. An appropriate amount of SiO 2 nanospheres still features a highly porous structure, imparting favorable liquid wettability, high mass uptake of electrolyte, and superior ionic conductivity. Accordingly, the sol–gel deposition method is believed to attract interests for applications in Li-ion batteries due to its simplicity, effectiveness, and multi-functionality.

Hygrothermal behaviour of timber frame walls finished with a brick veneer cladding

In this study, two typical timber frame walls with brick veneer cladding have been constructed at KU Leuven to investigate the hygrothermal response of these constructions in a moderate sea climate. Main topic of research is the contradictory criterion for the wind barrier when it comes to the risk on interstitial condensation for winter and summer conditions: in winter a vapour open wind barrier is appropriate, in summer a more vapour tight. Therefore, similar walls but with different types of wind barrier have been investigated. In one set-up a vapour open bituminous impregnated wood fibre board is used as wind barrier, whereas in the second set-up a more vapour tight wood fibre cement board is used. The study shows that a high relative humidity can be expected at the interface between insulation and wind barrier during winter conditions, leading to a high mould growth index. In contrast, the relative humidity at the interface between insulation and inner vapour retarder during summer is lower than expected. This can be caused by the buffering capacity of the hygroscopic materials in the wall.

Long term monitoring of repaired external wall assembly

This study discusses on hygrothermal performance of external wall assembly based on long term observation on relative humidity and temperature in layered external wall assembly, when the resistance of water vapor in insulating material is higher than in the main framing of the studied building. In this case the location of the vapor barrier must be examined more closely.In 1974 completed building the facade of the building was made from concrete and bricks. The external wall assembly was repaired by replacing the thermal insulation and facade brickwork. The original brick-insulation-brick structure was unventilated like those used to be until mid-1980s. The repaired outer layer was constructed with a ventilation gap which satisfies the building codes in force. Old thermal insulation was replaced with aluminum foil backed polyurethane insulation. The aim of the study was to verify that the new structure was performing properly by measuring the circumstances inside the new external wall assembly. The performance of the repaired external wall was monitored by sensors installed in four depths and in five different locations in the building. Each of the sensors measured relative humidity and temperature for two years.The repaired external wall assembly was observed to be performing correctly. The aluminum foil backed polyurethane insulation functioned as planned as wall assembly’s thermal insulation and vapor barrier. Condensation of the indoor air into the structure was not detected during the measurement period. Neither was the outside air’s relative humidity condensed outside the vapor barrier during the measurement period. There was no observation of the condensation neither in the ventilation gap, nor in the fire resistant mineral wool layer during the measurement period, in any inside or outside circumstances.

Highly Reliable Cu Wiring Layer of 1/1 μm Line/Space Using Newly Designed Insulation Barrier Film

Abstract The interposer or fan-out packaging technology with ultra-fine line/space has been required in order to achieve high density interconnection between chips with low cost. In this paper, we propose the iBF (insulation barrier film) to satisfy the insulation reliability of 1/1 μm ultra-fine trench wiring. The features of iBF are very low moisture absorptivity less than 0.3%, chloride ion impurities less than 1.0 ppm and high resistance to hydrolysis. In addition, iBF has good adhesive strength to Ti and Cu. The trench wiring was fabricated for mechanical and insulation reliability evaluation using photosensitive dielectric, then covered with iBF. The obtained trench wiring with 2/2, 1.5/1.5 and 1/1 μm line/space has passed the reliability tests such as moisture sensitivity level 2, thermal cycling test and biased HAST (highly accelerated stress test). We have also verified high resolution of photosensitive dielectric and fabrication of ultra-fine trench wiring on iBF to realize fine multi-layer wiring.

A very low concentration of polybenzimidazole film interleaved bismaleimide/diallyl bisphenol a system with outstanding improvement in impact strength and excellent allround properties

A very low concentration of thermoplastic polybenzimidazole (PBI) film interleaved bismaleimide/diallyl bisphenol A (BMI/DBA) system with sandwich structure was designed for the outstanding impact resistance. The effects of PBI film layers (0∼5) on the mechanical, thermal, dielectric properties and flame retardancy of BMI/DBA were investigated. BMI/DBA interleaved with 5‐layer PBI film demonstrates a 274% increase in impact strength relative to BMI/DBA, and exhibits higher fracture toughness, flexural strength and modulus than BMI/DBA. The improvement in the mechanical property for PBI film interleaved BMI/DBA system is mainly attributed to the combined effects of the effective energy dissipation of the sandwich structure and the good interfacial bonding between PBI film and the matrix. Due to the high thermal stability of PBI, the effective thermal insulation and electromagnetic field barrier of PBI film in the sandwich structure and the increase of the reacted CC in resin system, PBI film interleaved BMI/DBA shows better thermal property, much higher flame retardancy and lower dielectric constant compared to BMI/DBA. In addition, when the same amount of PBI is applied, BMI/DBA interleaved with PBI film exhibits much better comprehensive properties than BMI/DBA with PBI particles for the sandwich structure. POLYM. COMPOS., 39:4569–4580, 2018. © 2017 Society of Plastics Engineers

Understanding the Spin Transport in MgO–HfO2 Bilayer Insulating Barrier Magnetic Tunnel Junction

Understanding the Spin Transport in MgO–HfO₂ Bilayer Insulating Barrier Magnetic Tunnel Junction

Wilderness cold-exposure injuries: An African perspective

Cold injuries may be systemic (hypothermia) or local (frostbite or non-freezing cold injury). Hypothermia (core temperature of <35°C) is very common in South Africa, particularly in trauma patients, and conditions suitable for the development of local cold injuries frequently occur. Despite this, cold injuries are underdiagnosed, and many practitioners lack insight into the modern management of frostbite. Risk factors include low ambient temperatures, increased duration of exposure, trauma, immobility, intoxication or mental illness, lack of protective clothing or equipment, immersion, level of fitness, extremes of age, and ethnicity. Core temperature measurement should be obtained using an oesophageal probe in intubated patients, or a rectal thermometer in those who are conscious. Field management involves prevention of further heat loss by insulation and vapour barriers, and moving the patient to shelter. Rewarming strategies depend on the severity of hypothermia, and include core rewarming with heat packs, warm blankets and warm fluids (orally or intravenously). Unconscious victims of severe hypothermia require careful handling, advanced airway management and invasive rewarming, which may include extracorporeal means. Local cold injuries should be protected and rewarmed in a warm-water bath as soon as they are no longer at a risk of refreezing. Warming should be completed before grading and prognostication. Surgery should be deferred in almost all cases. Intra-arterial thrombolysis and prostacyclin-analogue infusions are novel therapies which may prevent tissue loss.

Adipose tissue: between the extremes.

Adipose tissue represents a critical component in healthy energy homeostasis. It fulfills important roles in whole-body lipid handling, serves as the body's major energy storage compartment and insulation barrier, and secretes numerous endocrine mediators such as adipokines or lipokines. As a consequence, dysfunction of these processes in adipose tissue compartments is tightly linked to severe metabolic disorders, including obesity, metabolic syndrome, lipodystrophy, and cachexia. While numerous studies have addressed causes and consequences of obesity-related adipose tissue hypertrophy and hyperplasia for health, critical pathways and mechanisms in (involuntary) adipose tissue loss as well as its systemic metabolic consequences are far less understood. In this review, we discuss the current understanding of conditions of adipose tissue wasting and review microenvironmental determinants of adipocyte (dys)function in related pathophysiologies.

Transport and Magnetoresistance in Topological Insulator-Based Ferromagnetic/Insulator/Ferromagnetic Junction in the Presence of External Electric Field

Using Landauer-Buttiker formalism, thin barrier approximation, and Klein tunneling theory, the effects of external electric field and induced exchange magnetic gap on the conductance and specifically magnetoresistance (MR) of a topological insulator-based ferromagnet/insulator/ferromagnet (TI-based F/I/F) junction have investigated. Conductance and MR for parallel (P) and antiparallel (AP) magnetic gap configurations are obtained and discussed. The results of MR reveal a significant negative value for maximum magnetic gap at z = (n + 3/4)π (n = 0, 1...), i.e., in smaller insulator barrier strengths in the presence of an external electric field, while it appears at z = nπ (n = 1, 2...) without electric field in Ref. Linder et al., Phys. Rev. Lett., 104:067001, 2010 (z is the barrier strength). Also, we have found that maximum transmission probability (TP) increases with magnetic gap in the presence of electric field which is one for P case in z = (n + 1/6)π and approaches to one for induced magnetic gap near the Fermi energy for AP case in the absence of electric field and z = (n + 1/2)π. Finally, the conductance and MR oscillate with the magnetic gap and barrier strength.