Enhancement of poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonate) properties by poly(vinyl alcohol) and doping agent as conductive nano-thin film for electronic application

In this work, the integration of the useful concepts of polymer blending and doping agent to simultaneously improve various properties of poly(3,4-ethylene dioxy thiophene) poly(styrene sulfonate) (PEDOT:PSS) nano-thin films was shown. According to the polymer-blending concept, insulating poly(vinyl alcohol) (PVA) has a good deal of potential to be utilized as a filler to improve the critical properties of the PEDOT:PSS matrix, especially conductivity, wettability, and thermal and mechanical properties. At the appropriate amount of PVA, 0.08 wt%, it acts as a binder to improve the connection network between PEDOT:PSS chains, leading to a maximum conductivity of 1.18 S/cm, and also providing a good contact angle of 8.8°. The transmission of the films decreased with increasing PVA content; however, all specimens still showed excellent transmittance values of more than 80 %. The thermal stability and the resistance to abrasion of the nano-thin conductive films were improved by strong covalent bonds between PVA and PSS, which were verified by TGA and a scratching test, respectively. In addition, the relationship of PEDOT:PSS properties versus various amounts of insulating PVA for practical usage for specific electronic fields were shown. Use of the doping agent quinoxaline was aimed to particularly enhance the conductivity of PEDOT:PSS. The highest conductivity (2.75 S/cm) was achieved when 0.5 wt% quinoxaline was added into 0.08 wt% PVA/PEDOT:PSS while the other properties were not significantly altered.     

Sol–gel route to carbon nanotube borosilicate glass composites

Dense borosilicate glass matrix composites containing up to 3 wt% of multiwalled carbon nanotubes were produced by a sol–gel process. The three different silicate precursors employed (tetramethylsilane (TMOS), methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS)) yielded transparent xerogels which were subsequently crushed and densified by hot pressing at 800 °C. The dispersion of the carbon nanotubes was aided by using an organic–inorganic binder (3-aminopropyl triethoxysilane) which limited flocculation of the CNTs in the silica sol. After densification, the borosilicate glass composites containing up to 2 wt% CNTs showed significant improvements in hardness and compression strength, as well as thermal conductivity, whilst percolation effects lead to a dramatic increase in electrical conductivity above 1 wt%. This simple approach to disperse CNTs into a technical silicate glass matrix via the sol–gel process focusses specifically on the borosilicate system, but the procedure can be applied to produce other inorganic matrix composites containing CNTs.     

聚乙烯醇纤维增强钢渣粉-水泥复合材料基本力学性能及微观结构

通过掺加钢渣粉来制备聚乙烯醇（PVA）纤维增强钢渣粉-水泥基复合材料,从宏微观两个方面研究了这种复合材料的性能。考虑了基体材料的水胶比（0.25和0.35）、不同钢渣粉质量分数（0、30wt%、60wt%、80wt%）,采用抗压强度试验、薄板四点弯曲试验研究了PVA纤维增强钢渣粉-水泥基复合材料的基本力学性能变化规律及其在弯曲荷载作用下的裂缝控制能力,采用扫描电镜观测了破坏后试样的微观结构。结果表明,水胶比和钢渣粉掺量均可明显影响PVA纤维增强钢渣粉-水泥基复合材料的基本力学性能,在低水胶比条件下（水胶比为0.25）,钢渣粉掺量达到80wt%时,试样表现出较高的韧性指数和良好的裂缝控制能力,基本满足工程所需强度要求,水胶比为0.35时钢渣掺量不宜超过60wt%;同时,从节能减排的角度考虑,利用钢渣粉制备PVA纤维增强钢渣粉-水泥基复合材料是可行的。      

Microstructure and properties of metakaolin-based inorganic polymer foams

A mixture of 70 % metakaolin and 30 % blast furnace slag powders, employed as the raw material, is mixed with different alkaline activating solutions in the production of metakaolin-based inorganic polymer foams (MIPF) with various densities ranging from 0.4 to 1.0 g/cm³ using a mechanical foaming process. The microstructures of metakaolin and slag powders, inorganic binder, and MIPF specimens are characterized by using XRD, FTIR, and image analyses. The effects of stirring time, water/binder ratio, and foaming agent on the properties of inorganic binders are also evaluated. Moreover, the pore size distributions, thermal and mechanical properties of the MIPF specimens are obtained by conducting a series of measurements and then compared with each other. Based on the experimental results, it is found that the measured cell length, cell wall thickness, compressive strength, flexural strength, and coefficient of thermal conductivity of the MIPF specimens are significantly affected by their densities.     

Influence of graphene nanoplatelets content on the structure and properties of macroporous carbon foams prepared by organic colloidal templates

Graphene nanoplatelets (GNPs)-reinforced carbon foams have been fabricated by polycondensation of resorcinol–formaldehyde resin as a carbon precursor and GNPs as a reinforcing material. The pore structure, mechanical properties, and electrical conductivity were investigated in terms of the amount of the GNPs. The results show that the amount of GNPs has a considerable influence on compressive strength, electrical conductivity, and specific capacitance. Although the amount of GNPs added does not influence the pore structure, the mechanical properties, electrical conductivity, and specific capacitance of carbon foams were improved with increasing the GNPs content. With 5 wt% addition of GNPs, the compressive strength, electrical conductivity, and specific capacitance increased by 75.2, 240.26, and 53.36 %, respectively.     

Silica ceramic nanofiber membrane with ultra-softness and high temperature insulation

Silica ceramic nanofiber (SCNF) membranes with ultra-softness were fabricated by electrospinning and precursor derived ceramic technology. Firstly, the precursor fiber membrane was obtained by electrospinning from spinnable precursor sol, which was prepared by using silica sol as raw material and polyvinyl alcohol (PVA) as spinning aid, and after heat treatment, it was converted into the SCNF membrane composed of pure inorganic components, which had the ultra-softness to restore the original shape after arbitrary folding. Then the effects of different PVA dosages and heat treatment temperatures on the fiber morphology, thermal stability, mechanical properties, and thermal conductivity of SCNF membranes were investigated. Among all the membranes, the SCNF membrane that was made with a precursor sol of 5% PVA and sintered at 900 °C (Ss?+?PVA 5%-900 °C) showed the smoothest as well as the most uniform fiber morphology, with an average fiber diameter of 285.19 nm, a density of 0.106 g cm^?3, the best mechanical properties (tensile strength of 4.145 MPa), and it also had the lowest thermal conductivity of 0.05285 Wm^?1 K^?1. The Ss?+?PVA 5%-900 °C SCNF membrane still maintained intact fiber morphology after being treated at 1200 °C. These excellent properties make the SCNF membrane have a potential application prospect as an insulation material in ultra-high temperature environments.

     

Physico-chemical properties of Bismuth nitrate filled PVA–LiClO<Subscript>4</Subscript> polymer composites for energy storage applications

A series of polymer composites were prepared by the addition of Bismuth nitrate (Bi(NO₃)₃) and Lithium perchlorate (LiClO₄) to poly(vinyl alcohol) (PVA) polymer matrix by solvent casting method. The microstructures and surface morphology were systematically characterized by FTIR spectroscopy, X-ray diffraction, AFM and SEM analysis. The DSC thermal studies exhibit the transformations in the composites due to the effect of Bi(NO₃)₃. The mechanical strength, ac and dc conducting properties were studied. The variation of ac conductivity of the composites with frequency follows Jonscher’s universal power law and found to be increased with increasing temperature. The sample containing 10 wt% Bi(NO₃)₃ exhibits good mechanical strength, high conductivity and dielectric constant at room temperature. The variation of conducting properties of 10 wt% Bi(NO₃)₃ filled composite with temperature has been explained based on hopping mechanism. The frequency exponent (s) have been well fitted with the proposed correlation equation of the barrier hopping model. The transport parameters are estimated using Rice and Roth model. The activation energy is calculated for the sample PVA–LiClO₄ matrix filled with 10 wt% Bi(NO₃)₃ using Arrhenius equation.     

Formation of self-aggregated and interconnected silver network within sol–gel silica

Interconnected silver network inside a sol–gel silica was formed by heat treating a nanoporous sol–gel silica sample containing 10–14 wt% silver ion and minimum of 34 wt% polyethylene glycol and polyvinylpyrrolidone (PVP). This hybrid material was initially translucent when dry, became dark-brown color after exposed to light, and then turned into silver metallic solid after heat-treated at 160 °C. The formation of silver network did not result in sample disintegration. Instead, we found the silver network enhances the compressive modulus of the sample. AFM and SEM images reveal that the unique topographic structures of the silver layer and the silica matrix are related to the amount of polymers. The interconnectivity of the silver structure at the sample surface was assessed by its electrical sheet resistance, which is ~0.003 Ω/sq. The results show that polymer-blended sol–gel silica materials can be used as an alternative template to synthesize interconnected silver network.     

高性能PVA纤维增强水泥基复合材料单轴受拉特性

高韧性PVA纤维增强水泥基复合材料具有很高的能量吸收能力,但强度通常较低,采用我国地方材料资源和工业废料,可制备出高强度同时极限变形量满足实际工程要求的高性能PVA纤维增强水泥基复合材料(HPFRCC),以应用于高层抗震建筑结构的关键部位。通过单轴受拉强度和变形特性试验,研究PVA纤维体积率、粉煤灰掺量、硅灰掺量、水胶比及砂胶比对HPFRCC抗拉性能的影响,研究结果表明:随着PVA纤维体积掺量的增加,HPFRCC的抗拉强度与极限拉应变增大;大掺量粉煤灰替代水泥及增大水胶比可降低HPFRCC的抗拉强度,但明显改善其受拉应变硬化特性;HPFRCC中掺入适量硅灰及细砂可提高其抗拉强度,但极限拉应变降低,尤其当砂胶比较大时,HPFRCC的受拉应变硬化现象不明显;基于细观力学模型,分析了各因素对HPFRCC拉伸应变硬化特性影响的原因,研究结果可为今后HPFRCC的实际工程应用提供基础依据。     

Flame retardance and thermal stability of wool fabric treated by boron containing silica sols

In order to improve flame retardance and thermal stability of wool fabric, a series of boron doped silica sols were prepared from a tetraethyl silicate inorganic precursor and applied to wool fabric as a flame retardant finish through the sol–gel process. Boric acid, zinc borate and ammonium borate were used as flame retardant additives. The effect of the boron containing flame retardant doped sol coatings on flammability, combustion behavior and thermal property of treated wool fabric was investigated via limited oxygen index (LOI) test, vertical burning test, thermogravimetric (TG) analysis, micro-calorimeter combustion (MCC) and smoke density test. It was found that the coatings on wool fabric acted as a heat insulation barrier, increasing the carbon residue and slowing down the spread of flame when burning, thus improving the flame retardance and thermal stability of the treated fabric. Meanwhile, the smoke density result indicated that the NH₄HB₄O₇ doped silica sol treated fabric had good smoke suppression property. Furthermore, the result of mechanical properties showed that there was no damage on tensile strength and air permeation of treated wool fabric.     

Improving the thermal and mechanical properties of silicone polymer by incorporating functionalized graphene oxide

Functionalized graphene oxide (FGO) was produced by reacting graphene oxide nanosheets with vinyl trimethoxy silane (VTMS). The results confirmed the attachment of VTMS molecules to the surface of GO sheets by Si–O–C bonding. The introduction of VTMS molecules led to an excellent dispersibility in tetrahydrofuran and to the complete exfoliation of FGO with a thickness of about 1.19 nm. Meanwhile, FGO/silicone polymer composites were prepared by solution blending method. The incorporation of 0.5 wt% of FGO in silicone polymer improved remarkably the thermal stability, tensile strength, and thermal conductivity of the silicone polymer composite, due to the homogeneous dispersion of FGO in the composites as well as to the strong interfacial adhesion with silicone polymer matrix. Tensile strength and thermal conductivity of the FGO/silicone polymer composite were increased by 95.6 and 78.3 %, respectively, with the addition of 0.5 wt% FGO. The 5 % weight loss temperature of the composite at 0.5 wt% FGO loading was detected 26.1 °C higher than that of silicone polymer.     

Effect of polyethylene glycol on the mechanical property, microstructure, thermal stability, and flame resistance of phenol–urea–formaldehyde foams

In this study, polyethylene glycol (PEG) was added to phenol–urea–formaldehyde foam to improve its toughness, and the effects of PEG, with different molecular weights and dosages, on the mechanical property, microstructure, thermal stability, and flame resistance of phenol–urea–formaldehyde foam were studied. The addition of PEG significantly increased the toughness and impact strength and decreased the pulverization rate of the foam. The compression strength of the foam first increased and then decreased with increasing amounts of PEG. When 2 wt% PEGs were added, the compression strength of foams was the highest. The addition of PEG significantly influenced the microstructure of phenol–urea–formaldehyde foams, in which the cell diameter decreased and wall thickness increased with increasing amount and molecular weight of PEG. The addition of PEG also slightly decreased the thermal stability of phenol–urea–formaldehyde foams, and increased the heat release rate, total heat release, and total smoke release of the foams.     

Briques silico-calcaires autoclavées: influence de l’addition de laitier de haut fourneau sur la formation des phases

The mechanical properties of sand-lime bricks produced by autoclaving under different conditions and incorporation of granulated slag have been investigated previously. In this study, the relationship is established between the structure, the phases formed and the strength. Based lime and granulated slag a new binder is developed. This is cured at saturated vapour pressures of 1.0 and 1.8 MPa. The results showed a decrease in compressive strength due to the substitution. The microstructure analysis showed that reaction products consist mainly of 11 Å tobermorite and xonotlite. Also, when increasing the autoclave temperature, it results in an increase in xonotlite relative to tobermorite. The X-ray diffractions of these phases are very low, hardly visible; they are masked by the presence of quartz. Their intensities increase with the presence of slag. The slag seems more reactive with lime than quartz. Observations with the scanning electron microscope allow better to appreciate these phases. By its composition to amorphous structure, the granulated slag does not release new distinct phases of hydrates.     

膨胀石墨/酚醛树脂-聚乙烯醇缩丁醛复合双极板的制备与性能

采用聚乙烯醇缩丁醛（PVB）对酚醛树脂（PF）进行改性,并以膨胀石墨为第一导电填料,用模压成型法制备了新型质子交换膜燃料电池用膨胀石墨/PF-PVB复合材料双极板。研究了PVB与PF质量比、改性树脂含量及炭黑的添加对膨胀石墨/PF-PVB复合材料双极板电导率、抗弯强度等性能的影响。结果表明,当改性树脂质量分数固定为30wt%时,膨胀石墨/PF-PVB复合材料双极板在PVB：PF=0.5时表现出最佳的电导率及抗弯强度,分别为192.3 S/cm、47.25 MPa,与不添加PVB的膨胀石墨/PF复合材料双极板相比,平面内电导率和抗弯强度分别提高了12.3%、14.2%。在PVB含量固定的条件下（PVB：PF=0.5）,当改性树脂的质量分数由25wt%增加至45wt%时,膨胀石墨/PF-PVB复合材料双极板的电导率下降,而抗弯强度增加。进一步添加炭黑提高膨胀石墨/PF-PVB复合材料双极板的导电性能,当改性树脂质量分数固定为45wt%时,炭黑添加量为4wt%的试样表现出最佳的平面电导率和面比电阻,分别为137 S/cm、14.4 mΩ·cm²。     

Aqueous tape casting of yttria stabilized zirconia

Tape casting process was used to produce yttria stabilized zirconia (YSZ) substrates in an aqueous system with poly(vinylalcohol) (PVA) and glycerine as binder and plasticizer, respectively. Various compositions of YSZ slips with different amounts of PVA and glycerine and consequently different solid/liquid ratios were prepared. The influence of the slip composition on the rheological properties of the slips was studied. In addition, the effect of the slip composition on the properties of the green and sintered tapes was investigated. PVA and glycerine did not affect the dispersion properties of the YSZ powder. Glycerine additions enhanced the flexibility of the green tapes but also produced a decrease in the tensile strength. The increase in the PVA content increased the tensile strength but resulted in a markedly decrease in the green density of the tapes. A correlation between the green and sintered density was found. The anisotropic sintering shrinkage parallel and perpendicular to the casting direction increased with increasing the PVA content. The slip compositions with 5 wt% PVA produced green tapes with satisfactory tensile strength. They had the highest sintered density, the lower sintering shrinkage and the lesser shrinkage anisotropy.     

Proton conductivity of Nafion/ex situ Stöber silica nanocomposite membranes as a function of silica particle size and temperature

In the first systematic study of the influence of the size of silica particles on ion exchange capacity (IEC) and proton conductivity of Nafion–silica nanocomposite membranes, thin films cast from mixtures of silica particles (5 wt%) with varying diameters ranging from 10 to 400 nm and Nafion in alcohol were examined. IECs decreased exactly as expected with the dilution of Nafion and its sulfonic acid groups with added silica. At 80 °C, the proton conductivity was also less with silica particles. However, at higher temperatures (120 °C), there was a 58 % improvement in proton conductivity at low relative humidity and a 45 % improvement at higher relative humidity for nanocomposite membranes prepared with silica particles <50 nm in size. The improvement was less significant with larger silica particles in the membranes.     

Phosphorus-containing silane modified steel slag waste to reduce fire hazards of rigid polyurethane foams

Steel slag (SS) waste was microencapsulated by a 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-derived silane via sol–gel reaction to improve its compatibility with polymer as well as to enhance flame retardant efficiency. The modified steel slag (mSS) was combined with expanded graphite (EG) as flame retardant system for rigid polyurethane foams (RPUFs). The RPUF-3 sample with 10 wt% mSS and 10 wt% EG showed an optimal comprehensive performance including a compressive strength of 206.9 kPa, a thermal conductivity of 0.0304 W/(m·K), a limiting oxygen index (LOI) value of 24.0% and UL-94 V-0 classification. The peak heat release rate (pHRR) and total heat release (THR) of the RPUF-3 dropped by 55% and 47%, respectively. By comparison, the RPUF-6 sample with 10 wt% SS and 10 wt% EG exhibited poorer flame-retardant behaviors. The superior flame retardancy of RPUF-3 over RPUF-6 could be ascribed to phosphorus-silicon complex in mSS promoted charring that provided better barrier effect during combustion.     

Alkali-activated slag-blended cements with silica supplementary materials

This paper presents results of detailed studies of composite slag binders with mineral silica additions differing in reactivity. We have identified general trends and assessed the effects of composition, particle size, and binder hardening conditions on the normal consistency, paste setting time, hardening kinetics, strength, average density, and water absorption in composite slag binder stone. Using X-ray diffraction and scanning electron microscopy, we have identified the key features of structure formation in stone with mineral silica additions and examined the influence of additives on the composition and volume of the hardening products of composite slag binders. The results have been used to construct a model of the structure and structural elements of composite slag binder stone with mineral silica additions.     

Use of Ti in hard metal alloys – Part II: mechanical properties

WC‐Co hard metal is a material of high hardness, high compressive strength and wear resistance while maintaining good toughness and thermal stability. Samples of nanosized WC powders with 10 wt% Co, WC‐10 wt% Ti, WC‐9 wt% Ti‐1 wt% Co were cold pressed at 200 MPa and sintered at 1500°C during 1 hour under vacuum of 10^–2 mbar. The characterization of the sintered materials was performed by the measurements of densification, HV30 hardness, fracture toughness and compression strength. The results showed that it is possible to process a hard metal through a Powder Metallurgical conventional route from nanoscaled WC grains, using Ti (or a Ti‐Co mixture) as a binder phase, with good mechanical properties.     

The hydration and microstructure of ultra high-strength concrete with cement–silica fume–slag binder

This study investigated the flowability, compressive strength, heat of hydration, porosity and calcium hydroxide content of ultra-high-strength concrete (UHSC) with cement–silica fume–slag binder at 20 °C. The composition of the binder was designed using seven-batch factorial design method. The relationships between the binder composition and the properties were expressed in contours. Results showed that proper silica fume content could improve the flowability and compressive strength of UHSC, reduce the porosity and calcium hydroxide content of UHSC. Slag reduced the flowability, compressive strength, porosity, and calcium hydroxide content of UHSC to certain extent. The silica fume and slag demonstrated positive synergistic effects on the flowability and 3 d compressive strength, but have negative synergistic effects on the total heat of hydration, hydration heat when the time is infinitely long(P₀), 56 d compressive strength, porosity and calcium hydroxide content of UHSC.