Colloidal and Chemical Processes in Hardening Alkaline Compositions Based on Aluminosilicates and Slags: 1. Control of the Properties of Alkaline Compositions

Chemical interactions in aqueous concentrated compositions based on natural and technogenic aluminosilicates and binders are studied by the rheology and calorimetry methods. It is shown that small amounts of alkali cause the hardening of compositions. Concepts of controlling the properties of hardening compositions by the addition of corresponding alkalis are developed.     

A Study of the Hydration of Lime-Pozzolan Binders

DTA/TG and TG/DTG thermal studies and XRD investigations were carried out on pastes of lime-pozzolan binders to examine the relative hydration process. The binders were prepared with two natural pozzolans and hydrated lime, mixed together in different proportions. The main hydrated phases formed in the pastes are calcium silicate hydrate (CSH) and mono-carboaluminate. The growth of CSH was greater for the paste of the pozzolan richer in reactive constituents. For pastes with a higher lime/pozzolan ratio, a slowing of the formation of CSH was observed, while the formation of monocarboaluminate was more intense. The calcium hydroxide contents of the pastes obtained by thermogravimetric analysis made it possible to determine the pozzolanic activities of the two pozzolans under examination. The mortars for the various lime-pozzolan binders displayed characteristic hardening. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationship between the Structure of Cement Stone and the Parameters of Ice Formation during Stone Freezing

The specific features of ice formation during freezing of hardening binders are considered as dependent on the structural characteristics. The theoretical grounds for the relationship between the crystallization point of the pore-confined liquid and the pore size are discussed. The possible mechanisms of frost-caused cement stone destruction and the conditions of their development are considered. A model is proposed for estimating the danger of ice formation. The results of experimental studies are given for ice formation during freezing of tricalcium silicate and tricalcium aluminate. The parameters of ice formation are shown to be interrelated with the properties of the porous structure formed during hardening of these binders. The laws characterizing the degree of danger due to ice formation during freezing of cement stone are established.     

Metallochlorophosphates-Perspective Binders for Heat Resistive Compositions

Abstract

New ways of synthesizing aluminium, magnesium and chromium phosphate binders with phosphorous metal ratio of 1:l were discovered. It was found that the viscous solution of met-allochlorophosphate binders and powdered chlorophosphate aluminium, magnesium and chromium can be used as a component for heat resistive materials. Viscous binders increase the mechanical strength, while powdered chlorophosphates ensure safe storage, usage and transportation. Investigation of formation conditions, constituent, pnysico-chemical properties and thermal treatment of liquid binders and precipitated from it aluminium, chromium and magnesium chlorophosphate showed the presence of MHPO₄ · nH₂O where M-Al, Cr and MgH₂PO₄Cl·nH₂O where n = 2–6. It was found that similar compounds are formed by the reaction of metallic chloride with phosphoric acid and metallic hydrooxide, the mixture of phosphoric and hydrochloric acids having M:P:Cl = 1:1:1.1–1.8 ratio. The latter method is more technological. It was stated that the viscosity, density and stability of liquid chlorophosphate binders depend on the nature of cations: viscosity increases, while density decreases from Cr-Mg-Al, precrystallization period increases from 1 to 3 days for magnesium up to 3–5 months for aluminium, and a year for chromium. As a result of thermal treatment metallic orthophosphate without water of crystallization is produced. Highly effective heat resistive materials with compressive strength of 70–106 MPa, refrectoriness 1300–1800°C oped. ?1800°C and hardening temperature of 150–350°C are developed.     

Adhesive-Strength Evaluation via the <Emphasis Type="Italic">Pull-Out</Emphasis> Method in a Binder—Elementary-Filament System at Various Treatments of Filaments

The adhesive strength of binders with elementary filaments that have been used for the production of LUP carbon tape covered by different types of coatings is evaluated via the pull-out method. Two types of single-layer coatings are considered, one of which is based on titanium of the VT1-0 brand while the other is made of 12Kh18N10T steel, as well as a bilayer coating composed of a titanium layer coated by a stainlesssteel layer. The adhesive strength is determined for thermoreactive (epoxy with amine hardener) and thermoplastic (polyamide) types of binders. The best adhesive strength (more than 30%) of binders is achieved when the LUP carbon tape is covered with stainless steel.     

Preparation and properties of wooden fiberboards with phenol cardanol formaldehyde adhesives

The results of a study of wooden fiberboards, for which phenol cardanol formaldehyde resins with different cardanol content were used as binders, are shown. The influence of technological factors on the bending strength of fiberboards and their water absorption in the case of the use of such binders is shown.     

Experimental investigation on the mechanical properties of Cyperus pangorei fibers and jute fiber-based natural fiber composites

The present era uses natural fibers as a partial replacement for synthetic fibers, thereby utilizing eco-friendly materials in a number of automotive applications (namely, bumpers, wind shields, doors, ceilings, etc.). Although there are many research findings related to natural fiber composites, in this work, a new sandwich layer of Cyperus pangorei fibers and jute fiber epoxy hybrid composites is developed using the hand lay-up technique and compared with the pure Cyperus pangorei fiber and pure jute fiber epoxy composites. The mechanical properties like tensile, flexural, compressive, impact, and hardness are performed as per ASTM standards for the developed composites. The test results show that Cyperus pangorei hybrid composite 3 had a tensile strength of 50.2 MPa, flexural strength of 301.48 N mm^?2, ultimate compression load of 15.03 KN, impact energy of 6.34 J, and Shore D hardness of 82.7, which are superior by 1.1–1.5 times to all the other developed composites. The microstructural characterizations are performed using scanning electron microscope which played a vital role in analyzing the failure morphology of the composites.     

Synthesis of new colloidal formations during the strengthening of different activated hydrated metallurgical slags

This paper reports on a comparison of experimental researches on the hydration hardening of different types of dumped ferrous slag (DFS) (blast furnace, open hearth, electric steel and converter), non-activated and activated with small (2%) additions of Portland cement or lime. Activation was found to accelerate the strengthening processes in the early stages of hydration resulting from the growth of colloidal sol–gel new formations in a more alkaline environment. Over time, these formations became denser and transformed into stone-like amorphous materials with a uniaxial strength of up to 47.6 MPa at 1 year of age. All these types of slag can, therefore, be used in different applications, for example, like traditional binders, such as Portland cement, to different ceramic goods, new construction materials, etc. But till now the results of this research were used only for the preparing of binder materials for natural soils strengthening as road bases in Russia. Highways whose roadbeds were built with these DFS as binder materials have shown excellent performance indices in different parts of Russia, including Siberia and northern regions.     

锂离子电池高电压正极粘结剂的研究进展

锂离子电池在高电压下会导致严重的电解液分解以及不稳定的正极与电解质界面问题,严重制约高电压正极材料的商业化.粘结剂不仅可以将正极活性材料和导电炭紧密粘结在集流体上,还对构建电解质与正极之间的多尺度相容性界面起积极作用,因此,粘结剂的优化可以有效解决上述难题.本文提出了高电压锂离子电池正极粘结剂需具备的必要条件,如:粘结性能和机械性能优异,具有出色的电化学稳定性和热力学稳定性以及良好的离子和电子传输能力等.综述了近些年来高电压正极粘结剂的研究及发展现状,通过天然粘结剂和合成粘结剂对目前已报道的高电压粘结剂进行了评述,介绍了各种粘结剂对电极的粘结性能和包覆以及对锂离子电池性能的影响机制,重点阐述了粘结剂分子结构中的极性基团与活性物质间的相互作用,如氢键和离子-偶极相互作用,并讨论了设计开发高电压正极粘结剂的途径以及展望了高电压正极粘结剂的发展前景.     

Bench-Scale Testing of Zinc Ferrite Sorbent for Hot Gas Clean-up

Advanced integrated gasification combined cycle (IGCC) power generation systems require the development of high-temperature, regenerable desulfurization sorbents, which are capable of removing hydrogen sulfide from coal gasifier gas to very low levels. In this paper, zinc ferrites prepared by co-precipitation were identified as a novel coal gas desulfurization sorbent at high temperature. Preparation of zinc ferrite and effects of binders on pore volume, strength and desulfurization efficiency of zinc ferrite desulfurizer were studied. Moreover, the behavior of zinc ferrite sorbent during desulfurization and regeneration under the temperature range of 350-400℃are investigated. Effects of binders on the pore volume, mechanical strength and desulfurization efficiency of zinc ferrite sorbents indicated that the addition of kaolinite to zinc ferrite desulfurizer seems to be superior to other binders under the experimental conditions.     

Element-containing fibers with epoxy binders: Structures and properties of hardened compositions

New types of composites based on element-containing carbon fibers (ECFs) and an epoxy binder have been developed. The results show that the presence of functional groups within the ECF structure affects significantly the reaction mechanism of the epoxy matrix. Connections between processes occuring in the interphase zone (the boundary layer) and the properties of hardened composites have been revealed. The factors controlling the binder hardening reactions occuring on surfaces of interphases when creating composites with improved physical and mechanical properties as well as with predermined service properties (polishing, anion-exchange, anti-corrosion, flame-resistance, controlled range of electrical resistance etc) are defined. A potential for using ECFs in a role unusual for them, namely as hardeners for epoxide binders, has been established. Applications of reactive ECFs which may function both as a filler and as a hardener provides longer service life of the composites and minimizes the amount of volatile products released in the process of hardening.     

Study on the evaluation of mechanical and thermal properties of natural sisal fiber/general polymer composites reinforced with nanoclay

Composite materials, made by replacing traditional materials, are used because of their capability to produce tailor-made, desirable properties such as high tensile strength, low thermal expansion, and high strength to weight ratio. The need for the development of new materials is essential and growing day by day. The natural sisal/general polymer (GP) reinforced with nanoclay composites has become more attractive due to its high specific strength, light weight, and biodegradability. In this study, sisal–nanoclay composite is developed and its mechanical properties such as tensile strength, flexural strength, and impact strength are evaluated. The interfacial properties, internal cracks, and internal structure of the fractured surface are evaluated using scanning electron microscope. The thermal disintegration of composites are evaluated by thermogravimetric analysis. The results indicate that the incorporation of nanoclay in sisal fiber/GP can improve its properties and can be used as a substitute material for glass fiber-reinforced polymer composites.     

Morphology, flexural, and thermal properties of sepiolite modified epoxy resins with different curing agents

A bisphenol A-based epoxy resin was modified with 5 wt% organically modified sepiolite (Pangel B40) and thermally cured using two different curing agents: an aliphatic diamine (Jeffamine D230, D230) and a cycloaliphatic diamine (3DCM). The morphology of the cured materials was established by scanning and transmission electron microscopy analysis. The thermal stability, thermo-mechanical properties, and flexural behaviour of the sepiolite-modified matrices were evaluated and compared with the corresponding neat matrix. The initial thermal decomposition temperature did not change with the addition of sepiolite. The flexural modulus of the epoxy matrix slightly increases by the incorporation of the organophilic sepiolite. The flexural strength of the sepiolite modified resin cured with D230 increased by a 10% while the sepiolite modified resin cured with 3DCM resulted in a lower flexural strength compared with the unmodified resin. The reduced flexural strength was attributed to the stress concentrations caused by the sepiolite modifier, which rendered the resins more brittle.     

Effect of internal mold release agent on flexural and inter laminar shear properties of carbon and glass fabric reinforced thermoset composites

The study is focused on thermoset composites reinforced with carbon and glass woven fabrics. Two types of thermoset resins, for example, epoxy and vinyl ester were used as the matrix. Varying concentrations of internal mold releasing (IMR) agent was used in the resin. The composites were cured both at room temperature and at 80°C. The flexural properties were studied using 3‐point bending test method. Further theinter‐laminar shear strength (ILSS) was investigated using the short beam shear strength test based on 3‐point bending. The flexural modulus of room temperature cured epoxy resin is higher than that of high temperature cured epoxy resin and cured vinyl ester resin. The flexural modulus is lowest for 1% IMR sample in epoxy system and the modulus for 0% and 2% epoxy are not significantly different. Lowest flexural strength and modulus can be observed for the combination of reinforcement and curing conditions for samples containing 1% IMR for the epoxy systems. Carbon fiber is found to be less compatible with the vinyl ester resin system and the addition of IMR to the resin degraded the properties further. Inter‐laminar shear strength for epoxy‐based composites is not much affected by presence of IMR, but in case of vinyl ester based composites there is a decrease in ILSS on addition of IMR agent. The study explains variation in flexural properties on addition of IMR and change of curing conditions. These results can be used for ascertaining variation in mechanical properties in real use.     

Stacking sequence effect of aramid–UHMPE hybrid composites by flexural test method: MATERIAL PROPERTIES

Aramid fibre–ultra-high modulus polyethylene (UHMPE) fibre interply hybrid composites were fabricated with changes in the stacking sequence. The flexural strength and modulus of hybrid composites were measured in order to investigate the effect of stacking sequence. Scanning electron microscopy (SEM) was used to examine the fracture surface of interply hybrid composites. When aramid fibre was at the compressive side and dispersion extent of fibers was small, the higher flexural strength and positive hybrid effect were observed. In addition, the different stacking sequence resulted in a change in flexural failure mechanism which had an effect on the flexural strength. As the dispersion extent of fibers decreased, the introduction of cohesive failure in aramid–aramid interface and PE–PE interface improved the flexural strength of hybrid composites.     

A study of structure formation in a binder depending on the surface microrelief of carbon fiber

A correlation between the specific surface of carbon fibers and strength of the boundary layer in a binder has been established. The effect of fibers on the structure formation of a binder has been explained as being a result of the density of fiber reticulation. Its important influence on the rheological properties of binders has been established using the example of carbon fibers. Fibers with a low density of reticulation are shown to affect considerably the structure formation of binders.     

Biocomposites based on poly(butylene succinate) and curaua: Mechanical and morphological properties

Biocomposites based on poly(butylene succinate) (PBS) and curaua fibers have been produced by compression molding, and investigated as a function of fiber length and amount. Mechanical tests, water uptake and morphology studies were carried out in order to assess the composite features according to the characteristics of the reinforcing agents. It turns out that the impact and flexural strengths increase with fiber content. Moreover, the fiber length, varying from 1 to 4 cm for the composite reinforced with 20 wt% of fiber, influences impact strength, which is higher for shorter than for longer fibers. However, flexural strength is not greatly influenced by the length of the fibers. Water uptake studies reveal a higher sensitivity of the material to fiber content rather than fiber size. Biocomposites, which are characterized by enhanced mechanical properties as compared to PBS, can have different applications, for example in rigid packaging or interior car parts.     

Effect of glass transition temperature of polymeric binders on properties ceramic materials

In the paper are presented the studies of the effect of glass transition temperature of new water-thinnable polymeric binders on the properties of ceramic materials obtained by die pressing. The parameters of ceramic samples comprising polymeric binders have been compared with those of samples comprising poly(vinyl alcohol) (PVA) — water-soluble binder. When using poly(acrylic-styrene) (AS), poly(acrylic-allyl) (AA) and poly(vinyl-allyl) (VA) water-thinnable binders, materials of greater density and mechanical strength were obtained in the green state as well as after sintering than those in the case of using PVA. The dependence of the chemical structure of the binders applied on the properties of samples such as the glass transition temperature and hydrophobic-hydrophilic balance of the copolymers has been discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Experimental Investigation of Mechanical Properties of Golden Cane Fiber–Reinforced Polyester Composites

The main objective of this article is to introduce a new natural fiber as a reinforcement in polymers for making composites for lightweight applications. The extraction of golden cane (Chrysalidocarpus lutescens) fiber and the mechanical properties of the fiber-reinforced polyester composites are described. The composites were formulated up to a maximum volume fraction of 0.43, resulting in a mean tensile strength and modulus of 2.13 and 2.26 times and mean flexural strength and modulus of 1.94 and 2.89 times greater than those of plain polyester, respectively, at a higher volume fraction of 0.43. The work of fracture in impact is measured to be 358 J/m. The results of this study indicate that golden cane fibers have potential as reinforcing fillers in plastics in order to produce inexpensive materials with high toughness.     

Solid state NMR investigation of antiplasticization of polystyrene by mineral oil

The effects of mineral oil plasticization of polystyrene were investigated as a function of polystyrene molecular weight and mineral oil concentration. Solid state NMR, thermo/mechanical methods and positron annihilation spectroscopy (PAS) were used to study the molecular dynamics and free volume effects of this blend. Antiplasticization was observed in the low (40,000) molecular weight polystyrene samples as an embrittlement of the system. In contrast, the flexural modulus was not affected by the presence of mineral oil in the higher (270,000) molecular weight polymers but a decrease in the flexural strength was observed with increasing mineral oil concentration. The NMR and PAS data indicated that the mineral oil was not dissolved in the polymer at ambient temperature, rather it phase separated even at very low concentrations. This caused antiplasticization in low molecular weight polymers because the small free volume holes were filled causing a densification of the system. With high molecular weight polystyrene, this phase separation was manifested as a decrease in the flexural strength.