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Sphene (CaTiSiO5, i.e. CaO·TiO2·SiO2) ceramics were successfully developed via the polymer derived ceramics route, starting from a commercial silicone containing specific oxide fillers. The approach allowed the combination of synthesis, in conditions of high phase purity, and advanced manufacturing. In particular, the adopted starting materials enabled an easy preparation of pastes, to be used for direct ink writing (DIW) of three-dimensional reticulated scaffolds. Sphene scaffolds, after firing at 1300 °C, were always regular and crack-free, despite changes in the line spacing, resulting in variable porosity (from ≈ 59 to 74 %), and exhibited a compressive strength from 3.9 to 12.7 MPa. The porosity was actually hierarchical, considering the formation of ‘spongy’ struts. In vitro tests, with increasing immersion time in SBF solution, confirmed the bioactivity, combined with a quite slow ion release, useful to maintain the pH value at nearly physiological values. Additional biological tests, consisting of the seeding of scaffold with normal human adult dermal fibroblasts, showed adequate cell viability and no toxicity effect.

The present work was initiated to finalize resin for the development of thermal protection system (TPS) for the external surface of a polymeric composite rocket motor case made up of Carbon roving and Epoxy resin. The temperature on the outer surface of the composite case increases due to kinetic heating caused by aerodynamic drag and vehicle velocity. These rocket motor casings are functionally required only in the ascent phase of missile trajectory till motor action time and stage separation. Due to which the experienced heat flux is relatively less, and the temperature on the external composite case is in order of 250 °C - 300 °C depending on missile configuration & trajectory, unlike extreme thermal conditions on ablative nozzle liners exposed to rocket motor exhaust. The maximum allowable temperature in the present study for the Carbon-Epoxy case is 100 °C due to degradation in mechanical properties. The thermal protection system on the external surface will function as a heat-insulating layer based on the working mechanism of ablation. The resin of the thermal protection layer has a substantial impact on the manufacturing process and curing aspects, especially compatibility with the pre-cured carbon epoxy case layer. The generation of test results for thermal stability, cure characteristics and Tg for Epoxy resin has also been included in present studies as an additional objective that provides significant inputs for process development. The test results for Epoxy resin is also used as a basis for the finalization of resin for the thermal protection layer for processing aspects apart from its basic thermal stability characteristics. The ablative thermal protection working mechanism is based on the ablation phenomenon. In the case of ablation, resin plays a vital role due to pyrolysis and other thermal characteristics. In the present experimental studies, the Phenolic resin and Silicone resin are considered as candidate resin materials for ablative thermal protection system based on available literature and in house experience. The main objective of the present studies is to evaluate thermal stability, char yield after final decomposition through DSC and TGA techniques for both resins as these are fundamental characteristics needed for the present specific application. The test results for specific grades (formulation) of phenolic and Silicone resins are generated and compared. In the present work, the experimental studies to evaluate glass transition temperature (Tg), thermal stability, and cure characteristics for Epoxy resin is also carried through DSC. The test results of specific grade Epoxy resin provides a basis to assess thermal margins for resins selected for ablative thermal protection system and inputs for process development and design requirements. The scope of the present studies is aimed to finalize the resin system for external thermal protection of composite rocket motor case based on thermal characteristics test results and other compatibility aspects with the structural layer.

Various human motions yield stimuli from low-pressure (0–10 kPa) to high-pressure level (100–300 kPa). However, previous flexible pressure sensors are unable to detect various human motions from low to high-pressure stimuli, thus are unfavorable for the facile and integrated design of sensing system. Herein a novel flexible pressure sensor with a tunable and large pressure-detecting range is produced by simply infusing magnetic carboxyl iron particle (CIP)/silicone resin into carbon sponge (CS). Attributed to the magnetorheological effect, the upper pressure-detecting limit of the CS/CIP/silicone sensor in a frequency of 0.01–5 Hz is significantly increased from 180 to 330 kPa in the presence of magnetic field, while a lower pressure-detecting limit of 70 Pa is obtained in the absence of magnetic field, thus covering the whole pressure-detecting range for various human activities. The CS/CIP/silicone sensor in monitoring various human motions with low to high-pressure stimuli is demonstrated by recording breathing, arm movement, walking, lifting and grasping, consecutively. Characterized by high flexibility, low cost and easy manufacturing, the current strategy is highly provoking for the development of pressure sensors adapted to human motions of different pressure levels in a wide range.

A facial one-pot method for the preparation of phenyl silicone resins is introduced. Vinyl end-capped phenyl silicone resin (i) and phenyl hydrosilicone resin (ii) were successfully prepared by selecting trifluoromethanesulfonic acid (TfOH) as the catalyst. The structures and the thermo-optical performances of the resulting resins were investigated by IR, NMR, GPC, TGA and UV–Vis, respectively. The results show that the yield, the transparency and the refractive index for resin (i) are 95%, 90.4% and 1.5253, respectively, and for resin (ii) are 94%, 92.8% and 1.5201, respectively. The properties of the cake obtained by hydrosilylation of resin (i) and (ii) in the ratio of 1:1 for LED chip encapsulation were studied, and the packaging effect was examined preliminarily.

Thermo-physical properties of hollow glass microsphere (HGM) filled silicone resin are analyzed by various mathematical models to optimize the formulation for a low-density high-temperature resistant composite. The study involves analyzing effective thermal conductivity, specific heat, and density for a two-phase particulate composite system by using the most popular expressions available in the literature at various volume fractions of HGM in the silicone resin matrix. Experiments are performed to compare theoretical results with the experimental data and identified the preferred composition with a density as low as 0.39 g/cc and thermal conductivity 0.116 W/m-K. The microstructural studies by SEM are done to explain the deviation in experimental and theoretical results. FEM analysis is done to understand the heat flow phenomenon in HGM filled silicone composites.

In this paper we report epoxy molding compound lead frames (EMC-LFs) with encapsulated silicone as a simple and inexpensive packaging for AlGaN-based ultraviolet-B (UVB) light-emitting diodes (LEDs) displaying high light extracting efficiencies (LEE) and long operation lifetimes. The convex surfaces and beveled shapes obtained after curing the encapsulated silicone surrounding the UVB-LED chips significantly enhanced the light output power (LOP). With silicone present inside the EMC-LFs having bonding cavity diameters of 1.7 and 1.45 mm, the LOPs of the UVB-LEDs improved by 26 and 42%, respectively; reliability tests performed over a period of 1000 h revealed, however, that the LOPs decreased to 70 and 71%, respectively, of their initial values, but no cracks appeared in the silicone during such long-term operation. Thus, the stability of silicone-encapsulating EMC-LFs for UVB-LEDs was acceptable. When compared with AlN-based direct plating copper ceramic lead frames (AlN-DPC-LFs), our proposed packaging structure and method have the potential to lower the manufacturing cost of UVB-LEDs.

Purpose The purpose of this paper is to investigate the effects of structural parameters of fabric on thermal insulation properties of the coated fabric. Design/methodology/approach The authors established a numerical model for the ablation of silicone resin-coated fabric under high heat flow, and the simulation results have been validated by quartz lamp ablation experiment. The model was used to investigate the effects of structural parameters of glass fiber fabrics on the heat transfer process of the coated fabric. Findings The numerical values were in agreement with the experimental values. The thermal insulation of the coated glass fiber fabric was better than coated carbon fabric. Thermal insulation performance of the coated glass fiber fabrics was in order plain < 2/1 twill < 3/3 twill < 5/3 stain fabric. Increasing the warp density, from 100 to 180 ends/10 cm, the temperature of the back surface of the coated glass fiber fabric was reduced from 601°C to 553°C. Thermal insulation performance dramatically increased as yarn fineness went from 129 to 280 tex, and the temperature difference was 63°C. Research limitations/implications In the ablation process, to simplify the calculation, the combustion reaction of silicone resin was ignored, which can be added in the future research. Originality/value This paper provides the ablation model of the silicon-coated fabric based on the 3D geometry model to explore the influence of the structural parameters of coated glass fiber fabric on its thermal protection performance.

The high-temperature stability and thermal life of silicone resin-based potting compound (SC-3), used in the aerospace application for electrical insulation, is investigated Thermo-Gravimetry Analysis (TGA) in an inert environment. Nonisothermal TGA is performed in the temperature range of 30 °C to 900 °C at 10, 20, and 30 °C / min heating rates. The kinetic parameters such as activation energy and pre-exponential factor are obtained by the model-free method proposed by Kissinger-Akahira-Sunose (KAS) and Flynn Wall Ozawa (FWO) at various degree of conversion. The thermal degradation of the SC-3 compound is observed in the temperature range of 350 °C to 580 °C, and thermal endurance or time of failure of potting compound SC-3 is estimated as per ASTM E1877 standard. The results reveal that the potting compound SC-3 can be safely used continuously at 100 °C and for ~3.6 min at 350 °C. Experimental results are also useful to understand the degradation mechanism of the SC-3 compound.

Advanced metamaterials are designed upon the combination of (1) carbon nanotube (CNT) foam, which is obtained from chemical vapor deposition by fully consuming the initial nickel foam, and (2) nanosilver/silicone resin or graphene (Gr) foam. The CNT foam/nanosilver/silicone composite simultaneously exhibits a negative permittivity and permeability in the frequency range from 1 MHz to 1 GHz provided that the appropriate CNT foam amount is considered (20 m%). Double-negative performance in a similar frequency range is obtained with both 3/1 and 1/1 (mass basis) Gr/CNT-based composites. On the other hand, 3/2 (mass basis) Gr/CNT exhibits a negative permeability in the shared frequency range from 6 × 102 MHz to 1 GHz with still negative permittivity in the full range. The Gr amount allows to control the frequency behavior, with a variation in absolute permittivity and permeability values and a switch between a concave and convex behavior. Hence, the work contributes to the further expanding of the application range of metamaterials.

Purpose The purpose of this paper is to study the ablative behavior of the silicone resin-coated carbon fabric (coated fabric) that will swell significantly during ablation. Design/methodology/approach The ablation experiments of three coated fabrics were conducted by quartz lamp radiant. Based on the experimental analysis, a numerical model was proposed for the coated fabrics to study the ablative process in term of the energy balance, mass conservation and thermal decomposition equations. Findings Results showed that the average relative errors between the simulated temperatures and experimental values of back surfaces of coated fabric 1, 2 and 3 were 10.01, 7.53 and 7.32%, respectively. The average density of silicone resin of coated fabric 1 was reduced by 47.96%, and the closer the distance from the heated surface was, the more the density decreased. The thermal conductivity and specific heat capacity of silicone resin of coated fabric 1 increased with time. Before 50 s, each decomposition rate curve showed an inflection point, at which the silicone resin decomposed most intensely. Research limitations/implications Based on experimental observations, the ablative behavior of the material with fixed expansion layer was simulated. In the further research, the moving expansion layer could be considered. Originality/value This paper provides the theoretical basis to evaluate the effectiveness of thermal protection materials that will swell during ablation.

This paper assesses methods for the fabrication of single-sided electrically conductive tape. Silicone resin, dichlorobenzoyl peroxide, and various types of carbon fillers were used to prepare pressure-sensitive adhesives. Various carbon black and graphene filler concentrations in the range 1 to 25 wt.% were tested, whereas for carbon nanotubes the range was 0.25 to 10 wt.%. The adhesion, shear strength, tack, and shrinkage of the prepared tapes were determined. The most important property of the resulting tapes is their electrical conductivity. By using carbon black as a filler, it was possible to obtain a conductivity of 4.3 × 10−3 S/m, with carbon nanotubes 1.4 × 10−01 S/m and with graphene 5.9 × 10−3 S/m. Such electrically conductive silicone self-adhesive tapes are not yet commercially available on the market, but are expected to be useful in the electronic industry for the bonding of various materials. In the available literature provides no information about the self-adhesives tapes based on silicone pressure-sensitive adhesices which exhibit electrically conductive properties.

Insulated silicone/alumina (Al2O3) composites with high thermal stability and thermal conductivity were fabricated, in which the silicone resin was fabricated by a hydrolysis and condensation reaction with triethoxysilane (MTES), dimethyldiethoxysilane (DMDES) and phenyltrimethoxysilane (PhTMS). When the Al2O3 loading was 80 wt.%, the composite had only a 1.2% weight loss at 390°C. When the volume ratio of the 10 μm Al2O3 powder to 0.5 μm Al2O3 powder was controlled at 7:3, the silicone resin-based composite had thermal conductivity of 1.18 W m−1 K−1, which is 6.2 times as high as that of the pure silicone resin. Furthermore, the silicone/Al2O3 composite had dielectric strength of 87.5 kV mm−1.

Silicone resins are hyperbranched macromolecules, which are nearly spherical in shape, nanometer in size, and covered with numerous terminal organic groups. For this reason, they can play a role of functionalized silica nanoparticles that are miscible with a polymer medium. In this paper, mixtures of linear polyisobutylene (PIB) with methyl-terminated silicone MT resin are considered. The phase states of mixtures were studied by laser interferometry method accompanied with rheological tests. It turned out that the solubility of the silicone resin in PIB matrix does not exceed a few percent even at high temperatures. Nevertheless, the addition of the resin significantly reduces the effective viscosity of PIB due to the shear-induced interlayer slip. To describe the concentration dependence of the blend viscosity, various empirical equations were considered, and their combination to describe the viscosity of blends in different phase states by one equation was proposed.

Transparent flexible silicone materials are useful in electronics, sensors, coatings, and so forth. However, to the best of our knowledge, the tensile strength of unreinforced silicone rubber is lower than 0.4 MPa, and the highest tensile strength of highly transparent silicone-modified materials is no more than 1.5 MPa. The poor mechanical property limits their further application in electronic devices. Here, a kind of UV-cured transparent flexible silicone materials with tensile strength as high as 2.2 MPa were prepared by a UV-initiated thiol–ene reaction of a sulfur-containing hyperbranched polycarbosilane and a thiol silicone resin. Interestingly, their tensile strength can increase from 2.2 to 5.6 and 5.7 MPa after being immersed in an aqueous solution of 10 wt % hydrochloric acid and 10 wt % NaCl for 7 days, respectively. It is argued that the increase of the tensile strength of cured films may be attributed to the −SiOCH3 of the residual 3-trimethoxysilylpropanethiol in the sulfur-containing hyperbranched polycarbosilane. The performances of the cured materials were investigated in detail. These silicone materials exhibit transparency higher than 95% (wavenumber in the range of 400–800 nm), and the initial thermal decomposition temperatures of the cured materials are about 340 °C. These materials also show good anticorrosion property, and the mass loss of the materials immersed in the aqueous solution mediums is no more than 0.39 wt % even for 15 days.

In this article, an organosilicon antisticking coating was synthesized from vinyl silicone oil, hydrogen-containing silicone oil, and platinum catalyst. Firstly, the methyl vinyl MQ (mono and quad) silicone resin was added. When the silicone content was 30 wt.%, the shore hardness and tensile strength increased to about 27.4% and 115.9%, respectively. Furthermore, nano-SiO2 powder was added to further improve its antisticking property. This was due to the change of the surface roughness, which could greatly improve the antisticking performance. When the nano-SiO2 powder content was 2 wt.%, the surface free energy and antisticking force were the lowest and the antisticking effect was the best as well and the mechanical properties of silicone rubber had been improved.

Carbon nanotube (CNT) foams with negative permittivity and permeability are successfully prepared by chemical vapor deposition (CVD) and post-treatment. A double negative metamaterial in the 1–1000 MHz frequency range with double continuous structure results by effectively compounding the CNT foam with a polymer material, i.e. epoxy or nanosilver silicone resin. The negative permeability is specifically attributed to the three-dimensional CNT interactions as clear from the study of the relation of the material microstructure and the macroscopic measurements. Compared to CNT foam/epoxy composites, CNT foam/nanosilver/silicone composites have a lower permeability but a more excellent electrical conductivity or permittivity. It is also shown that the carbon source time during CVD and post-pressurization can be adjusted to allow for both negative permittivity and permeability. This contribution highlights a convenient method to obtain a metamaterial in a much larger frequency range (ca. 1 to 1000 MHz) than the state-of-the-art. It thus supports the expansion of the application range of metamaterials and simplifies their preparation, which is of great significance for the wider use of these materials.

In this paper, we report an AlN-based ceramic lead frame (LF) with encapsulating silicone between the surface of an AlGaN-based ultraviolet-B light-emitting diode (UVB-LED) chip and a quartz glass cover, the light output power (LOP) of this structure was 13.8% greater than that of the corresponding packaging structure without encapsulating silicone. Another packaging structure in which the silicone fully filled the cavity of the AlN-based ceramic LF included covering with quartz glass, in this case, the enhancement of the LOP was 11.7%. Reliability tests performed over a period of 3500 h at a forward current (If) of 100 mA revealed that the LOPs of these two silicone-containing packaging types decreased to 45.3 and 48.6%, respectively, of their initial values. The different degradation rates of these UVB-LEDs were not, however, correlated with the appearance of cracks in the encapsulating silicone during long-term operation. Excluding any possible mechanisms responsible for degradation within the UVB-LED chips, we suggest that the hermetic cover should be removed to avoid the appearance of cracks. Moreover, the main mechanism responsible for the slow degradation rates of LOPs in these proposed packaging structures involves the encapsulated silicone, after cracks have appeared, undergoing further deterioration by the UVB irradiation.

A novel silicone resin (SR-OH) containing phenolic hydroxyl (Ph–OH) groups was designed and synthesized via co-hydrolysis/condensation and catalytic hydrogenation. During the curing process, the cross-linking degree of the resin was further increased by the Si–O–Ph bonds formed by the reaction of the Ph–OH and terminal Si–OH groups. Thermogravimetric analysis (TGA) showed that the cured resin product exhibited excellent thermal and thermo-oxidative stability, which was much higher than that of a typical methyl phenyl silicone resin (SR-Ph). The temperature at which 5% weight loss occurs (Td5) was up to 606 °C (nitrogen) and 542 °C (air), and its char yield at 800 °C was 91.1% and 85.3% in nitrogen and air, respectively. The significant improvement in thermal stability was mainly attributed to the formation of Si–O–Ph bonds which not only increases the cross-linking degree of the resin but also significantly prevents degradation by the ‘back-biting’ and oxidative cleavage.

A series of epoxy modified methyl phenyl silicone resins with different epoxy values were prepared by an approach of combination of hydrolytic sol-gel and non-hydrolytic sol-gel process. Then, in order to solve poor compatibility between epoxy modified silicone resins and commercial amine curing agents, amine phenyl silicone resin curing agent was synthesized by non-hydrolytic sol-gel method. The test results exhibited that the process of combination of hydrolytic sol-gel and non-hydrolytic sol-gel process had a significant effect on the elimination of hydroxyl groups. A lot of experiments and mechanism analysis exhibited that the activity and content of hydroxyl groups are two important factors for ring-opening of epoxy groups and gelation of product. So, epoxy groups can be stably and efficiently introduced in the terminal of product in the course of non-hydrolytic sol-gel process, which hugely avoided ring-opening of epoxy groups. Subsequently, epoxy modified silicone materials were obtained by thermal curing reaction between epoxy modified silicone resins with different epoxy values and amine phenyl silicone resin. And the curing reaction can be completed at 80 °C for 2 h. Transmittance of light, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC) and reliability test were used to analyze performance of epoxy modified silicone materials. The results exhibited that prepared silicone materials had a high transmittance (>90%), strong adhesive strength, good thermal stability and mechanical performance. Therefore, epoxy modified silicone material can be applied in high-power LEDs packaging.

A series of high-refractive-index epoxy-modified vinyl methyl phenyl silicone resins with different content of vinyl groups have been synthesized by a combination of hydrolytic and nonhydrolytic sol–gel processes to improve their adhesion. The products were characterized by Fourier-transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. The results showed that epoxy and vinyl groups were successfully introduced into the products while the content of hydroxyl groups was low. Then, epoxy-modified silicone materials were manufactured by addition reaction between the epoxy-modified vinyl methyl phenyl silicone resins and hydrogen-containing phenyl silicone resin. The epoxy-modified silicone materials were characterized by thermal aging (250°C for 2 h) experiments, light transmittance measurements, thermogravimetric analysis, red dye penetration tests, reflow soldering (270°C for 10 cycles), and lumen depreciation (50 mA for 165 h) tests. The results showed that the epoxy-modified silicone materials exhibited high transmittance (> 90%) and good thermal stability. The epoxy-modified silicone materials showed better resistance to high temperature and ultraviolet (UV) radiation than commercial epoxy resin (6103). The introduced epoxy groups greatly improved the adhesion of the silicone resin. The epoxy-modified silicone material prepared using epoxy-modified vinyl methyl phenyl silicone resin with higher content of vinyl groups showed better mechanical performance (50 Shore D). The epoxy-modified silicone material EVMPS-3′ is expected to be applicable in packaging of high-power light-emitting diodes (LEDs).

Over the last 15 years, bulk hydrophobic treatment of cementitious materials with silanes and siloxanes is in the scientific focus. They are beneficial in terms of reducing water uptake by capillarity, however, this is often followed by an impact on cement hydration leading to the decrease in structural properties of cement matrix. The aim of this paper is to study the influence of different incorporation modes of a silicone-based hydrophobic agent used for the bulk hydrophobic treatment of mortars, and to evaluate their effect on cement hydration and the early age properties. Two different incorporation modes are compared: an emulsion of silane and silicone resin and microencapsulation of silicone resin. Each of these is incorporated in mortars prepared with CEM I and CEM III/A. Based on the combined measurement of isothermal calorimetry, electrical resistivity, ultrasonic pulse velocity, compressive strength, thermal expansion coefficient and autogenous deformation at early age, it is shown that the emulsion, as a delivery method of hydrophobic agent, affects the early age mechanical behavior of cement-based systems, for both types of cements. The microencapsulation on the other hand, prevents these effects from occurring, and is therefore suitable for bulk hydrophobic treatment.

Silicone resin is a high-temperature resistant material with excellent performance. The improvement of its thermal stability has always been the pursuit of researchers. In this paper, a sequence of silicone resins containing trifluorovinyl ether groups were prepared by the co-hydrolysis-polycondensation of methyl alkoxysilane monomers and {4-[trifluorovinyl(oxygen)]phenyl}methyldiethoxysilane. The structures of the silicone resins were characterized by FT-IR and 1H NMR. The curing process of them was studied by DSC and FT-IR spectra, and results showed that the curing of the resins included the condensation of the Si-OH groups and the [2 + 2] cyclodimerization reaction of the TFVE groups, which converted to perfluorocyclobutane structure after curing. The thermal stability and thermal degradation behavior of them was studied by TGA and FT-IR spectra. Compared with the pure methyl silicone resin, silicone resins containing TFVE groups showed better thermal stability under both N2 and air atmosphere. Their hydrophobic properties were characterized by contact angle test. Results showed that PFCB structure also improved the hydrophobicity of the silicone resin.

UV&ndash, curable polyacrylate is widely used in free&ndash, radical type UV&ndash, cure coating systems, the disadvantages of which including poor thermal stability and UV resistance can be overcome through chemical modification by silicone. However, it is a remarkable fact that the strategies for fabrication UV&ndash, cured silicone modified polyacrylates are somewhat complicated and the price of the products may be much expensive than pure UV&ndash, cured polyacrylates. In this work, an easy fabrication method to prepare inexpensive UV&ndash, cured transparent silicone modified polyacrylate coatings with good adhesion and UV resistance performance was developed from copolymers of acylates and thiol silicone resin by UV initiated thiol&ndash, ene click reaction without UV initiator. The striking results with a high application value should be emphasized that when the amount of thiol silicone resin is only one wt.% of the copolymer of acrylates, the UV&ndash, cured coatings obtained exhibit fairly good performance. These coatings prepared exhibit transparency higher than 96% (800 nm), adhesion property to glass slides can reach grade 0, pencil hardness can reach 6H, water absorption is less than 0.16%. In particular, it is observed obviously that the silicone modified polyacrylate coatings exhibit better UV resistance performance than the coating prepared with only copolymers of acrylates initiated by UV initiator 1173. It is proved that it is actually an easy fabrication method to prepare inexpensive UV&ndash, cured transparent silicone modified polyacrylate coatings with high performance by UV initiated thiol&ndash, ene click reaction of copolymers of acylates and thiol silicone resin.

In this study, corrosion-resistant composite coatings were produced by incorporating zinc (Zn) nanoparticles in an epoxy resin and a hybrid silicone resin. While performing sodium chloride saltspray tests, the corrosion performance of the nano-composite coatings was evaluated by applying these corrosion-resistant composite coatings on a carbon steel substrate. The nano-composite coatings on the substrates were characterized by an adhesion test, scanning electron microscope (SEM), and transmission electron microscope (TEM) with energy-dispersive X-ray spectroscopy (EDX). The results of the salt-spray tests showed that the Zn nanoparticles in the epoxy and hybrid silicone resins could react with permeated oxygen, thereby improving the anticorrosion properties of the Zn nano-composites. The corroded area of the epoxy resin samples decreased from more than 80% without Zn doping to less than 5% in a 3000-ppm Zn-doped sample after a 500-h saltspray test. An evaluation of the bactericidal properties showed that the Zn/epoxy and Zn/hybrid silicone resin nano-composites with at least 360 ppm of Zn nanoparticles exhibited bactericidal ability, which remarkably increased with the Zn nanoparticles content. The corrosion-resistant properties improved with the addition of Zn nano-composites coatings.

The first successful direct 3D printing, or additive manufacturing (AM), of heat-cured silicone meniscal implants, using biocompatible and bio-implantable silicone resins is reported. Silicone implants have conventionally been manufactured by indirect silicone casting and molding methods which are expensive and time-consuming. A novel custom-made heat-curing extrusion-based silicone 3D printer which is capable of directly 3D printing medical silicone implants is introduced. The rheological study of silicone resins and the optimization of critical process parameters are described in detail. The surface and cross-sectional morphologies of the printed silicone meniscus implant were also included. A time-lapsed simulation study of the heated silicone resin within the nozzle using computational fluid dynamics (CFD) was done and the results obtained closely resembled real time 3D printing. Solidworks one-convection model simulation, when compared to the on-off model, more closely correlated with the actual probed temperature. Finally, comparative mechanical study between 3D printed and heat-molded meniscus is conducted. The novel 3D printing process opens up the opportunities for rapid 3D printing of various customizable medical silicone implants and devices for patients and fills the current gap in the additive manufacturing industry. National Research Foundation (NRF) Published version This research is supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Medium-Sized Center Funding scheme and the NTU Start-Up Grant.

Crossing losses in silicone optical waveguides are related to the magnitude and spatial extent of the waveguide refractive index gradient. When processing conditions are altered, the refractive index gradient can vary substantially, even when the formulation remains constant. Controlling the refractive index gradient requires control of the concentration of small molecules present within the core and clad layers. Developing a fundamental understanding of how small molecule migration drives changes in crossing loss requires the ability to examine chemical functionality over small length scales, which is a natural fit for atomic force microscopy-infrared spectroscopy (AFM-IR). In this work, AFM-IR spectra from model bilayer stacks are initially examined to understand molecular migration that occurs from heating the core and clad layers. The results of these model studies are then applied to photopatterned waveguide builds, where structure-function relationships are constructed between values of crossing loss and the concentration of C-H and O-H functionalities present in the core and clad layers. Results show that small molecule evaporation and migration are competing processes that need to be controlled to minimize crossing loss.

Recently, various piezoresistive composites with good flexibility have been developed as sensing materials for flexible strain sensors (FSSs). External forces will be applied to strain sensors when they are used in some circumstances such as wrist bending, etc. However, conventional flexible composites may fail upon being subjected to external forces since they have low strength and are unable to protect the inner vulnerable structure of flexible sensors. In this work, the reduced graphene oxide-coated glass fabric (RGO@GF)/silicone composite is fabricated and used to make high-performance structural flexible strain sensors. The composite is not only flexible and sensitive to strain, but also exhibits the high tensile strength needed to maintain the structural integrity of the flexible strain sensor. Silicone resin and GF are employed to provide flexibility and high strength, respectively. By coating RGO on the surface of GF, the nonconductive GF becomes conductive, which renders the piezoresistive behavior and strain-sensing ability to the RGO@GF/silicone composite. The as-prepared structural flexible sensor not only possesses a good strain sensitivity with a gauge factor of around 113, which is much higher than that of typical strain sensors based on metals, but can also maintain its structural integrity until the applied external force is over 800 N, while the conventional flexible strain sensor fails upon being subjected to an external force of only 5 N. Moreover, the as-prepared structural FSS is applied to monitor wrist movement and breathing to demonstrate its applicability. Overall, the RGO@GF/silicone composite exhibits great potential as a sensing material for structural FSSs for wrist movement, etc.

Dual-activity silicone resins (DASR) with double bonds and epoxy groups were prepared via the hydrolysis and condensation of γ-glycidoxypropyltrimethoxysilane (γ-GPS) and γ-methacryloxypropyltrimethoxysilane (γ-MPS). The hydrolysis and condensation degree was monitored during the preparation process of DASR. The epoxy groups of DASR were directly reacted with amine groups on the fiber surface attempting to improve the interfacial properties of carbon fiber (CF) composites. The CF/DASR composites represented 36.91% and 20.85% enhancement in interfacial shear strength (IFSS), compared to those of MASR composites reinforced with untreated CF and amine modified CF. In addition, the tensile strength of CF/DASR remained stable after the UV irradiation. Thus, these attractive results demonstrate that the designed dual-activity silicone resin/carbon fiber composites provide a promising approach for preparing high-performance carbon fibers composites.

How to effectively enhance the tracking and erosion resistance of silicone rubber is a significant topic in high-voltage insulation. In this work, ureido-modified MQ silicone resin (UHMQ) was synthesized and employed to improve tracking and erosion resistance of silicone rubber in combination with platinum (Pt). The effect and mechanism of UHMQ/Pt on tracking and erosion resistance were studied via inclined plane test, leakage current curves, scanning electron microscopy, thermogravimetry and thermogravimetry-Fourier transform infrared spectrometry. When 5–7 phr of UHMQ and 0.33 phr of Pt catalyst were added, the tracking and erosion resistance of silicone rubber were greatly improved. In this case, all specimens passed the inclined plane test at 4.5 kV with low eroded mass and undamaged surfaces. The thermal stability of silicone rubber containing UHMQ/Pt was also much higher than that without, and the leakage current and discharging frequency on the surface of silicone rubber were markedly decreased with the introduction of UHMQ/Pt. This was attributed to UHMQ/Pt catalyzing radical crosslinking of silicone chains under arc discharging so that a protective barrier was established on the surface to resist arc ablation. Also, the enhanced radical mechanism suppressed degradation of silicone chains, and thus reduced release of cyclic oligomers which would aggravate arc discharging. Furthermore, since UHMQ/Pt facilitated complete oxidation of pyrolysis gases, the carbon deposit was reduced and tracking was suppressed.

This paper investigates the structure and magnetic properties of Ni-Cu-Zn ferrite-silicone coated iron-based soft magnetic composites (SMCs). Scanning electron microscopy coupled with a energy-dispersive spectroscopy (EDS) analysis revealed that the Ni-Cu-Zn ferrite and silicone resin were uniformly coated on the surface of iron powders. By controlling the composition of the coating layer, low total core loss of 97.7 mW/cm3 (eddy current loss of 48 mW/cm3, hysteresis loss of 49.7 mW/cm3, measured at 100 kHz and 0.02 T) and relatively high effective permeability of 72.5 (measured at 100 kHz) were achieved. In addition, the as-prepared SMCs displayed higher electrical resistivity, good magnetic characteristics over a wide range of frequencies (20–200 kHz) and ideal the D-C bias properties (more than 75% at H = 50 Oe). Furthermore, higher elastic modulus and hardness of SMCs, which means that the coating layer has good mechanical properties and is not easily damaged during the pressing process, were obtained in this paper. The results of this work indicate that the Ni-Cu-Zn ferrite-silicone coated SMCs have desirable properties which would make them suitable for application in the fields of the electric-magnetic switching devices, such as inductance coils, transformer cores, synchronous electric motors and resonant inductors.

In this study, vinyl-terminated polysiloxane (abbreviated VISR) and allyl-terminated polysiloxane (abbreviated ALSR) were synthesized and characterized. The curing behaviors and viscoelastic and thermal properties of VISR/PHSR and ALSR/PHSR were comparatively investigated. DSC and in situ FT-IR spectroscopy can be adopted to study the influence of molecular structures on reactivity. The results prove that ALSR/PHSR shows higher reactivity including a higher reaction rate constant and cure degree than VISR/PHSR. Moreover, it is found that the Sestak-Berggren equation can adequately depict the cure kinetic model of silicone resin in hydrosilylation comparing the calculated results with experimental data. Additionally, DMA exhibits that the glass transition temperature and cross-linking density of ALSR/PHSR are much lower than those of VISR/PHSR, TGA data reveal that they have similar thermal stability as well as high char yield, and the decomposition energy ranges from 100 to 270 kJ/mol with increment of de...

This study focused on the importance of the interfacial adhesion in the zirconia (ZrO2)/silicone hybrids as the encapsulating material on the reliability of the LEDs. Surface-modified ZrO2 nanoparticles (m-ZrO2) with functional groups were prepared by a sol-gel reaction which could become reactive to the silicone resin. The produced m-ZrO2/silicone hybrid at 5 wt% had a refractive index of 1.569 at 633 nm and light transmittance of 98.9%. Moreover, the coefficient of thermal expansion was greatly reduced by the introduction of m-ZrO2 into the silicone resin. When using this m-ZrO2/silicone hybrid, the luminous flux of the LED was 10.1% higher than that using a neat silicone resin. Most importantly, the LEDs encapsulated with the m-ZrO2/silicone had the best performance under thermal shock among all the LEDs tested in this study, owing to its strong interfacial adhesion between the nanoparticles and matrix. Moreover, the thermal stresses developed in hybrids were calculated and found to agree with the performance evaluation of the encapsulated LEDs under thermal shock, in which the m-ZrO2/silicone hybrid had the lowest thermal stress. This study proposed that the m-ZrO2/silicone hybrid material with strong interfacial adhesion could be useful for the encapsulation of LEDs even under extreme thermal conditions.

A novel multiphasic ceramic composite was developed in the form of highly porous open-celled foams, starting from a silicone-based mixture, incorporating micro-sized fillers and fired in N2 atmosphere. Highly homogeneous mixtures were first foamed at 350 °C, in air, and later fired at 1100 °C. The process yielded a final ceramic with two silicate phases (wollastonite, CaSiO3, and diopside, CaMgSi2O6), embedded in an amorphous matrix, exhibiting a particularly remarkable compressive strength (exceeding 20 MPa), and a residual open porosity of about 65% (with pore diameters ranging between 300 and 500 µm). This result cannot be attributed to the formation of a homogeneous silicon oxycarbide (SiOC) matrix; on the contrary, the amorphous material surrounding the silicate crystals consisted of a nano-composite, with C domains immersed in a silicate glass phase. Very preliminary cell culture studies performed in vitro showed encouraging results.

A melt-based self-stratifying coating based on silicone/epoxy blend systems is reported as an easy-to-use, eco-friendly, and industrial favorable procedure. The powder forms of the silicone and epoxy resins were mixed either by dry-blending or co-melt-mixing processing method, and blends were electrostatically applied onto steel sheets and cured. Self-stratification of cured coatings with a thickness of 100 ± 30 μm occurred and was investigated by an adopted ATR-FTIR method and consolidated SEM-EDX and X-ray photoelectron spectroscopy. Fundamental studies on influencing parameters on phase separation and stratification in coatings such as surface tension, the mass ratio of silicone/epoxy resins, crosslinking reaction, and manufacturing processes were performed and discussed in detail. It is corroborated that the dry-blending of methyl substituent silicone resin with the high and medium molecular weight epoxy resins at a 1/3 mass ratio (silicone/epoxy) leads to a complete stratification structure (Type I), having the silicone phase located on the top of the coating and the epoxy phase towards the steel surface, resulting in good adhesion. 3/1 mass ratio of the silicone/epoxy blends led to the dispersion of epoxy droplets into the silicone matrix (Type IV) and 1/1 mass ratio, showed lateral phase separation morphology. The co-melt-mixing process was yielded the formation of a thin homogenous layer of silicone phase on the top surface of the coating and a mixture of large and small drops of silicone dispersed into the epoxy matrix (Type I–Type III). Finally, the protective properties of the silicone/epoxy self-stratifying coatings with different stratification structures were evaluated.

As the population ages, the number of elderly people walking outside is also expected to increase. Due to natural process of aging, a direct consequence is weakening of muscle strength, which in turn leads to a decrease in walking speed and increases the risk of falling. [1,2]The purpose of this study is to develop a soft material with a nonlinear mechanical response by Hybrid structural design using multiple materials, which can be applied as a shoe bottom material that supports keeping walk speed while reducing the risk of falling, and robot hands that resemble human fingers. Soft materials have been used in a wide scope of fields such as soft robotics, medicine, and welfare, because they are safer and closer to biological characteristics than conventional metallic materials. In this research, we focus on giving an extra-viscosity to silicone rubber by embedding a flow channel of viscous fluid.ExperimentIn this experiment, we fabricated 20 mm cubic silicone samples, having a flow channel in the central 15 mm cubic area, and evaluated the dynamic viscoelasticity of the samples. A water-soluble flow channel (Parallel crosses structure) model was 3D printed with an FDM 3D printer (QIDITECH X-pro) using polyvinyl alcohol (PVA) filament. Figure 1 shows the flow channel structure. In the XY-plane the beam structures are printed in parallel at equal intervals, and their orientation is rotated 90° with each layer. The channel model was fixed in the center of a mold, then silicone resin (Ecoflex00-30, Smooth-on) was poured and cured. After the curing, the silicone part is removed from the mold and dipped in water to dissolve the PVA flow channel model. The sample was fabricated in two pieces to enable smooth dissolution and diffusion by allowing the edges of the PVA part to expose the water. The dissolved hollow part in the silicone was filled with viscous fluid. (hydroxyl propyl cellulose (HPC 150~400, Wako) solution in water). When filling the viscous fluid, we used a manual centrifuge machine to apply high gravity for smooth entering of the viscous fluid and degassing.The fluid was colored with black pigment so that the fluid can be visually recognized through the translucent silicone part. Figure.1 and Fig.2 show optical images of fabricated samples.Table 1 Shows the details of fabricated samples.As an evaluation, we measured the viscosity-shear rate dependence of viscous fluids with a rheometer. (Anton Paar, MCR302). In addition, we fabricated a DMA testing machine capable of large deformation at low frequencies and measured the dynamic viscoelasticity of fabricated samples at 1 Hz and 5 mm deformation. Table.2 shows the Measurement results of the DMA test.Result and discussionIn this result, we verified that the tangent loss of the two samples embedded with a viscous fluid is larger than that of simple silicone rubber. The tangent loss of the fabricated sample (B) is the largest, suggesting that only the viscosity difference between the silicone and the fluid affects the tangent loss.We considered that the flow in the channel would cause viscous resistance and increase the tangent δ. However, we could not verify any significant tangent loss in the fabricated sample(A). We guess that the viscosity of the fluid is too high to occur fluid flow in the channel or/and the current flow channel structure easily dissipate the force so that viscous resistance is too low. In the future, we study how the channel structure and fluid filling volume rate affects the viscous resistance of the filled viscous fluid.In this conference, we will report the fabrication method and evaluation results of the fabricated samples.

In order to develop insulating materials for high-voltage direct current (HVDC) cable joints, silicone nanocomposites are prepared by mixing liquid silicone resin (LSR) with the surface-modified nano-SiO2 and the surface-modified SiC nanoparticles, and the effects of SiC nanoparticles on space charge behaviors of the silicone nanocomposites are studied. The hydrophilic surface of the fumed nano-SiO2 is modified into a hydrophobic surface by treating with an alkyl silane coupling agent in order to be uniformly dispersed in LSR, and the surface of the SiC nanoparticles is modified with a vinyl silane coupling agent in order to improve the interfacial characteristics through covalent bonds between SiC nanoparticles and LSR. LSR is mixed with the modified nano-SiO2 (20 wt%) and the modified SiC nanoparticle (0 wt%-9 wt%). To observe the even dispersion of the modified nano-particles in LSR matrixes, a transmission electron microscope is employed and it is found that nano-SiO2 and nano-SiC particles are somewhat uniformly dispersed regardless of their content. When an appropriate amount of semiconductive nano-SiC particles is uniformly dispersed in the LSR/SiO2 nanocomposite, space charges are evenly dispersed. Therefore, the HVDC breakdown strength of the LSR nanocomposite would increase. However, if nano-SiC is mixed in excess, the conduction paths are formed, therefore the HVDC breakdown strength would decrease. HVDC breakdown strength under positive polarity condition shows the maximum value, 99.8 kV/2 mm in the nanocomposite with 3 wt% nano-SiC, which means that the space charge distribution is optimal in the 3 wt% nano-SiC system. However, excessive nano-SiC adversely affects the HVDC breakdown strength.

Steel slag is the desirable substitution of natural aggregate in asphalt mixture. Nevertheless, the high-water absorption and heavy metal ions pollution are the primary problems of recycling steel slag. This study involved silicone resin to process the steel slag for preventing it from water and improving heavy metal ions leaching problems. The sealing effect of silicon resin on steel slag was also verified by the micro measurement. The results show that the leaching concentrations of all heavy metal ions were generally reduced after treatment of silicone resin. The solid silicone resin formed the airtight membranous on the steel slag surface and effectively improved the heavy metal ions leaching problems. The boundary of elements distribution between steel slag and silicone resin area are obvious, which indicates that the silicone resin effectively and completely seals the steel slag surface. The water absorption rates, adhesion and microstructure of steel slag were also improved by silicone resin. The organic asphalt and silicone exhibit superior adhesion due to the rule of the likes dissolve each other, and it isolates steel slag from water, and reduces the stripping risk of asphalt binder.

Quantum dots (QDs) have been widely applied in luminescent sources due to their strong optical characteristics. However, a moisture environment causes their quenching, leading to an inferior optical performance in commercial applications. In this study, based on the high moisture resistance of epoxy resin, a novel epoxy/QDs composite particle structure was proposed to solve this issue. Flexible luminescent films could be obtained by packaging composite particles in silicone resin, combining the hydrophobicity of epoxy resin and the flexibility of PDMS simultaneously. The photoluminescence and light extraction were improved due to the scattering properties of the structure of composite particles, which was caused by the refractive index mismatch between the epoxy and silicone resin. Compared to the QD/silicone film under similar lighting conditions, the proposed flexible film demonstrated increased light efficiency as well as high moisture stability. The results revealed that a light-emitting diode (LED) device using the composite particle flexible (CPF) structure obtained a 34.2% performance enhancement in luminous efficiency as well as a 32% improvement in color conversion efficiency compared to those of devices with QD/silicone film (QSF) structure. Furthermore, the CPF structure exhibited strong thermal and moisture stability against extreme ambient conditions of 85 °C and 85% relative humidity simultaneously. The normalized luminous flux degradation of devices embedded in CPF and QSF structures after aging for 118 h were ~20.2% and ~43.8%, respectively. The satisfactory performance of the CPF structure in terms of optical and moisture stability shows its great potential value in flexible commercial QD-based LED displays and lighting applications.

The thiol-epoxy click chemistry is promising for microelectronic packaging due to its outstanding properties, while there is little knowledge on silicone/epoxy composite fabricated via this approach. Herein, a thiol-functionalized silicone resin (MDT-SH) is synthesized and compounded with epoxy resin to form silicone/epoxy composite. The thermal-curing behaviors, mechanical properties and LED encapsulation of the developed composite are studied detailedly. The thermal-curing kinetics indicate that the thiol-epoxy polymerization in silicone/epoxy composite tends more to the first-order reaction and its active energy is about 60.3 kJ/mol. The mechanical properties of the composite are varied with the molecular structure of MDT-SH and thiol/epoxy ratio. Moreover, the composite has excellent transparency in visible region, and its transparency is little affected by thermal and UV ageing. More importantly, the transparency is only slightly decreased after the composite is serviced at normal temperature and pressure for 2 years. The light output power of LEDs encapsulated by this composite is comparable to the commercial counterparts like Dow Corning OE-6550, but its thermal-curing time and temperature are much lower than the latter, contributing to cost reduction. Therefore, this silicone/epoxy composite based on thiol–epoxy click chemistry would greatly improve the microelectronic packaging.

Iron-based soft magnetic composites with silicone resin coating have been designed to reduce the core loss and improve the magnetic properties of cores. The silicone resin serving as electrical insulating layer was modified by 3-glycidoxypropyltrimethoxy silane, and the effect of silicone resin content, coupling agent, annealing treatment, and thermal cycling on the magnetic properties of composites was investigated in the frequency range from DC to 150 kHz. The coated silicone resin insulating layer was characterized by scanning electron microscopy and energy dispersive spectroscopy. The results showed that the optimum coating content of silicone resin to attain the acceptable permeability and the minimum magnetic loss for the prepared composites is 4 wt%. The sample with silicone resin coat exhibited better DC-bias superposition characteristics compared to the uncoated sample, 6 wt% silicone resin coating sample have excellent percentage effective permeability (84.8%) under 50 Oe applied field. AC magnetic properties evaluated at 1 and 100 kHz do not vary with a 95% confidence interval with the number of thermal cycles; therefore, the properties of the silicone resin-insulating composites are stable under thermal cycling.

The mismatch of refractive index (RI) between light emitting diode (LED) chips and packaging resins severely lowers the lighting emitting efficacy of LED. The RI can be enhanced by the introduction of high RI nanoparticles but meanwhile it is a great challenge to maintain the high transparency for resins due to the agglomeration of nanoparticles. In this work, a facile strategy is proposed to fabricate silicone nanocomposites with a high transparency (>88%, less than 2% decrease relative to pure silicone resin), largely enhanced RI (an increase from 1.42 to 1.60) and improved thermal stability (73 °C increase in weight loss of 50%). Specifically, the ultra-fine monodispersed TiO2/silicone composites are prepared by direct solvent mixing of 1 wt% surface modified TiO2 nanoparticles (S-TiO2) into the silicone resin, in which S-TiO2 are prepared by direct introduction of titanate coupling agent in the process of TiO2 growth to induce the formation of protective layer on the surfaces of TiO2 nanoparticles. This methodology demonstrated is simple, cost-effective and versatile for the massive fabrication of highly transparent LED packaging materials with greatly enhanced refractive index and meanwhile enhanced thermal stability.

Cycloaliphatic epoxy resin was modified by phenyl methyl silicone resin to investigate the influence of silicone content on the performance and reliability of epoxy packaged light-emitting diode. The silicone modification of epoxy encapsulants was characterized by transform infrared (FT-IR) spectrophotometer. Rotational rheometer was used to study rheology behavior. Differential scanning calorimetry, thermogravimetric analyses, dynamic mechanical analysis, thermomechanical analyzer were introduced to measure the thermal and mechanical properties. Ultraviolet visible spectrophotometer was utilized to study heat and ultraviolet resistance. In reliability test, scanning acoustic microscope and scanning electron microscope were applied to observe interfacial delamination. Water sorption process was monitored using gravimetric measurement. FT-IR study shows a chemical bonding between hydroxyl group of silicone resin and epoxy resin. With the incorporation of silicone resin, favorable properties were obtained such as higher thermal decomposition temperature, lower equilibrium water sorption, and better heat and UV resistance. Among these systems, 10% silicone modified epoxy resin exhibits the best performance in reliability test.

Microwave (MW) processing was used to cure a sol-gel type silicone resin coating that normally requires thermal curing over 250 °C. The study focused on coatings applied on polycarbonate and poly(methyl methacrylate) substrates and processing temperatures did not exceed 100 °C when using Silicone Carbide, Carbon, and Aluminium susceptors at 5% concentration by weight. Heating performance of the susceptors in bulk silicone resin matrix as well as in thin layers was compared. The results presented show that the heating response of the additives measured in bulk was significant. However, results for thin layers indicated that the effects of MW heating on the coatings containing the susceptors were limited, and samples microwaved at 800 W for 4 h imparted insignificant increase of the coating hardness. This outcome was supported by AFM Phase images which revealed no distinctive layer near the susceptor particles. This suggests that the heat dissipation to the substrate and air with limited heating performance of the susceptors does not allow for an effective in-situ curing in thin layer.

Dow Corning® VE-6001 UV is a new silicone-based, ultraviolet curable optically clear resin, exhibiting high refractive index, low shrinkage, enhanced cure performance and stable reliability. It provides a reliable silicone solution for the fabrication of high quality display modules requiring long-term reliability, such as automotive displays.

In this paper, we prepared the light emitting diode (LED) encapsulant with self-adhesion and high refractive index. In order to improve adhesion properties, we synthesized a series of multifunctional polysiloxanes with different contents of epoxy groups via the sol–gel condensation of methylvinyldimethoxysilane, diphenylsilanediol and 3-glycidoxypropyldimethoxymethylsilane. The structures of epoxyphenylvinyl silicone (EPVS) resins were confirmed by proton nuclear magnetic resonance and Fourier-transform infrared. The effect of epoxy group content on the adhesion property of EPVS resins was fully studied. The performances of the LED encapsulation materials based on EPVS resins were investigated in detail. These self-adhesive encapsulating materials showed excellent thermal stability, a high refractive index of 1.55 and good adhesive property. These EPVSs can be used as an adhesion promoter for LED encapsulation materials. Copyright © 2017 John Wiley & Sons, Ltd.

The commonly used materials in fog seal are emulsified asphalt and modified emulsified asphalt. Nevertheless, there are some intractable problems including aging under ultraviolet, poor permeability, and moisture susceptibility. Therefore, silicone resin polymer was used as a kind of innovative fog seal material in this study. Physicochemical properties of solidified silicone resin were characterized. X-ray computed tomography and 3D reconstruction technology were used to evaluate permeability and distribution of silicone resin polymer in an asphalt mixture. Moisture sensitivity and high-temperature performance of the asphalt mixture maintained by silicone resin polymer were also detected. The results show that surface characteristic of silicone resin can effectively isolate moisture, thereby improving moisture resistance of the asphalt mixture. Silicone resin was found to be evenly distributed throughout the pores of a sample when the dosage was 400 or 600 mL/m2. The pore filling rate increased by 16.3% when the dosage was changed from 200 to 400 mL/m2, whereas it only increased by 3.7% when dosage increased from 400 to 600 mL/m2. Moisture damage resistance of asphalt mixtures generally increased as the dosage of silicone was increased. However, as the dosage increased from 400 to 600 mL/m2, the growth rate in residual Marshall stability (RMS) and tensile strength ratio (TSR) slowed significantly since the pore filling effect of silicone has reached the upper limit. Dosage of silicone resin has little effect on the results of the rutting test while it has significant influence on Hamburg wheel tracking test (HWT). Furthermore, it was found that 400 mL/m2 is the optimum silicone dosage for open-graded friction course (OGFC)-13 mixture in consideration of permeability, distribution, performance of mixture, and economic cost.

Traditional semiconductor packaging techniques and materials have been working well for conventional Si devices, which usually operate at temperatures up to 175 °C. As the operating temperature increases, these techniques exhibit failures such as bulk flows, volume shrinkage, brittleness and subsequent cracking, and deterioration of dielectric strength. For the new wide-bandgap power devices, which work at voltages as high as 1200 V and junction temperatures as high as 250 °C, there is currently no known dielectric material to encapsulate and protect the active devices. This paper summarizes novel solutions for high-temperature dielectric materials for encapsulating high-power semiconductor devices without any dielectric breakdown and also without introducing excessive thermal, electrical, and mechanical stresses to the encapsulated devices. Polymer dielectric candidates investigated in this paper include cyanate ester-based resin and silicone-based resin. In addition, conformal coating approaches that include alumina deposited by atomic layer deposition (ALD) technique and tetrahedral amorphous carbon (ta-c) deposited by filtered cathodic vacuum arc technique were evaluated in this paper. Dielectric strength performance of the material combinations with respect to temperatures was evaluated. Among the polymer encapsulants, a silicone resin with silica fillers was determined to be the prospective candidate. Breakdown voltage and leakage current of the silicone-based encapsulant with and without the conformal coating was measured by breakdown tests. It was determined that the ta-c conformal coating deteriorates the dielectric performance of the encapsulant, while the alumina thin film deposited by ALD approach reduces the leakage current of the encapsulation material and also increases the breakdown voltage of the silicone encapsulant. Thus, the combination of alumina thin film deposited by ALD approach along with the silicone encapsulant is recommended for this application, involving high temperature and high voltage. Agency for Science, Technology and Research (A*STAR) Accepted version This work was supported by the A*STAR Aerospace Consortium.