Heat-insulating composite based on unwoven materials and organomineral binder

Composites based on unwoven cellulose-hydrate and carbon materials and an organomineral binder have been developed and investigated. Optimal compositions of the composites feature a higher fire resistance, a low density, and effective thermophysical characteristics. The composites are promising for use as heat-insulating materials with a rigid structure in different branches of the national economy and industry. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 85–91, January–February, 2009.     

Pore- and micro-structural characterization of a novel structural binder based on iron carbonation

The pore- and micro-structural features of a novel binding material based on the carbonation of waste metallic iron powder are reported in this paper. The binder contains metallic iron powder as the major ingredient, followed by additives containing silica and alumina to facilitate favorable reaction product formation. Compressive strengths sufficient for a majority of concrete applications are attained. The material pore structure is investigated primarily through mercury intrusion porosimetry whereas electron microscopy is used for microstructural characterization. Reduction in the overall porosity and the average pore size with an increase in carbonation duration from 1 day to 4 days is noticed. The pore structure features are used in predictive models for gas and moisture transport (water vapor diffusivity and moisture permeability) through the porous medium which dictates its long-term durability when used in structural applications. Comparisons of the pore structure with those of a Portland cement paste are also provided. The morphology of the reaction products in the iron-based binder, and the distribution of constituent elements in the microstructure are also reported.     

High-performance carbon composite electrode based on an ionic liquid as a binder

Ionic liquid, n-octylpyridinum hexafluorophosphate (OPFP) has been used to fabricate a new carbon composite electrode with very attractive electrochemical behavior. This type of carbon electrode has been constructed using graphite mixed with OPFP as the binder. The electrode has combined advantages of edge plane characteristics of carbon nanotubes and edge plane pyrolytic graphite electrodes together with the low cost of carbon paste electrodes and robustness of metallic electrodes. It provides a remarkable increase in the rate of electron transfer of different organic and inorganic electroactive compounds and offers a marked decrease in the overvoltage for biomolecules such as NADH, dopamine, and ascorbic acid. It also circumvents NADH surface fouling effects as well as furnishing higher current density for a wide range of compounds tested. Depending on the choice of the electrolyte, the electrode can have the ion-exchange property and adsorptive characteristics of clay-modified electrodes. The proposed electrode thus allows sensitive, low-potential, simple, low-cost, and stable electrochemical sensing of biomolecules and other electroactive compounds. Scanning electron microscopy images indicate significant improvement in the microstructure of the proposed electrode compared to carbon paste electrodes. Such abilities promote new opportunities for a wide range of electrochemical and biosensing applications.     

High strength geopolymer binder based on waste-glass powder

This paper presents a study on the synthesis of geopolymers based on alkaline activation of waste-glass powder using aqueous solutions of sodium hydroxide and sodium silicate with different Na₂O contents as alkali activators. Three types of calcium aluminate cements were also incorporated into the dry binder at levels up to 24% by weight in order to modify the chemical composition of the geopolymer source materials. The prepared mortars were tested for workability, setting time, compressive strength, free-alkali content and tendency towards efflorescence formation. FTIR and SEM analyses were also performed to characterize the morphology and structure of the produced geopolymer. The optimized geopolymer mortar exhibited a remarkable maximum compressive strength of 87 MPa. The results showed that inclusion of calcium aluminate cements in the silica-rich waste-glass powder leads to release high amounts of reactive alumina into aluminosilicate gels, improving the geopolymerization reactions and resulting in the formation of a more cross-linked network that exhibits higher compressive strength. High alumina cement Secar 71 showed the greatest effect in strength enhancement due to the higher amount of reactive alumina releasing into the reaction medium. The findings demonstrate a new potential of value-added reuse application for waste-glass powder by adding a suitable amount of materials that are rich in reactive alumina.     

N100基聚氨酯弹性体粘合剂的合成及表征

采用傅立叶变换红外光谱技术和力学性能测试技术对P(E-CO-T)-N100体系的预固化反应动力学及其在交联改性双基推进剂粘合剂体系中的应用进行了研究.结果显示,P(E-CO-T)-N100体系的预聚反应时间是180min,同时获得了预聚率与预聚时间的关系,预聚180min后,-NCO的转化率为80%.根据"相似相溶"原理,预聚物与推进剂的主要组分NG、DEGDN和NC的溶度参数差△δ均＜2,说明P(E-CO-T)-N100预聚物具有良好的相溶性.P(E-CO-T)-N100预聚物的加入使粘合剂体系的交联密度从1.03×10-5提高到了2.17×10-5.常温下的力学性能数据显示,P(E-CO-T)-N100预聚物上的活性-NCO与NC上的-OH进行了交联,使粘合剂体系的延伸率达到191.7%,提高了74%.     

Extended pseudorandom sequences and two-dimensional coding collimators based on them

A new extensive class of one-dimensional binary sequences, called extended pseudorandom sequences, is proposed which enables a radiation-physics experiment to be optimized more completely and enables problems of planar emission tomography to be solved effectively using integral-code measuring systems. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 66–71, June, 2007.     

Extended ternary sequences and two-dimensional coding collimators based on them

A new extensive class of one-dimensional ternary (−1, 0, +1)-sequences, called extended ternary sequences, is proposed, which enables radiation-physics experiments to be more completely optimized and enables problems of emission planar tomography to be solved more effectively using code-based integrated measurement systems. __________ Translated from Izmeritel'naya Tekhnika, No. 8, pp. 62–68, August, 2008     

Thermophysical characteristics of aprotonic solvents and electrolytes based on them

Measured and computed values of the thermal conductivity and heat capacity of a number of organic solvents and electrolytes based on them are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 4, pp. 623–626, October, 1982.     

Radionuclide sorption diagnostics of nanoagglomerates and textures based on them

Diagnostics of nanoagglomerates of hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ and of hierarchic structures based on them by the method of adsorption of tritium-labeled sodium succinate is made. The adsorption kinetics is one-step in the case of hydroxyapatite nanocrystals and two-step in the case of textured hydroxyapatite. The parameters of the S-shaped sorption isotherms are calculated; they are described by the Guggenheim-Fowler-Frumkin equation. The specific surface area of hydroxyapatite nanoagglomerates is 650–700 m² g^?1, which is close to the theoretical density of individual nanocrystals (900 m² g^?1), and the specific surface area of textured hydroxyapatite (macrospheroids) is 250–300 m² g^?1. Adsorption of succinate ions on the surface of hydroxyapatite nanocrystals leads to the formation of a tightly bound monolayer, which may lead to structural rearrangement of the sorbent.     

Viscosity and density of aprotonic solvents and electrolytes based on them

The results of an experimental determination of the viscosity and density of organic solvents and electrolytes based on them are given.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 3, pp. 422–427, March, 1982.     

Chitosan as a tablet binder

Abstract

Chitosan was evaluated as a binder for chlorpheniramine maleate tablets in comparison with other cellulose binders such as sodium carboxymethylcellulose, hydroxypropylmethylcellulose and methylcellulose. The effects of binder concentration on the mechanical properties of granules and tablets as well as on disintegration time and dissolution profiles were studied. Results showed that granules prepared with methylcellulose had lowest percentage of fines and friability. Chitosan tablets showed best dissolution profiles. The rank order correlation for binder efficiency was: hydroxypropylmethylcellulose > chitosan > methylcellulose > sodium carboxymethylcellulose.     

Influence of the binder on the properties of catalysts based on titanium-vanadium oxides

The influence of the nature of the binder and its concentration in V₂O₅/TiO₂ catalysts on their mechanical and catalytic properties has been studied. The characterization analysis showed that the agglomeration mechanism is different when an inorganic acid, such as H₃PO₄, or a natural silicate, such as sepiolite, were used. Two different patterns are proposed, which explain the effect of these binders on the performance of this type of catalyst in the selective catalytic reduction of NO _x with NH₃.     

Evaluation of long-term effects of rejuvenation on reclaimed binder properties based on chemical-rheological tests and analyses

This study used multiple chemical-rheological tests to investigate the long-term characteristics of rejuvenating agents in reclaimed asphalt binders. To this end, a base binder and its blending with an extracted binder obtained from recycled asphalt pavements were selected, and two different types of rejuvenating agents: agriculture-based and petroleum-based agents were used to modify the blended binder. The base binder and the blended binders that were modified by the two rejuvenators were then aged using a typical laboratory long-term aging procedure. The chemical studies included: a saturates-aromatics-resins-asphaltenes analysis, Fourier transform infrared spectroscopy, and elemental (carbon, hydrogen, nitrogen, sulfur and oxygen) analysis. The rheological tests primarily investigated the linear viscoelastic properties through aging and rejuvenation. The effects of rejuvenators on restoration were quite material-dependent, which was related to the different chemical compositions of the rejuvenators and their chemical-molecular interactions with the parent binder. The tests and analysis results showed that the immediate effects of rejuvenators are mostly the result of the addition of lighter molecules in rejuvenators, while the long-term effects were material-specific and further chemistry-driven. From the two rejuvenating agents studied herein, the petroleum-based material improves performance of the binder in the next round of service by preserving the chemical composition and maintaining the stability, whereas the agriculture-based agent used in this study might increase the aging issues because of its pre-existing high oxygen content, which could negatively affect long-term durability over service period.     

Bisphenol A based polyester binder as an effective interlaminar toughener

Bisphenol A based thermoplastic polyesters are commonly used in the industry as binders, or tackifiers, to produce cost-saving preforms in Liquid Composite Moulding processes such as Vacuum Assisted Resin Transfer Moulding (VARTM). However, it is often reported that the presence of these polyesters has a detrimental effect on the mechanical properties of the resulting composite laminates. In contrast, this study shows that interlaminar toughness can be increased without negatively affecting other properties by coating the reinforcing plies with a bisphenol A based thermoplastic polyester if some precautions are taken in mind.The polyester was added to an epoxy resin in order to study its effect on the thermophysical properties and fracture toughness of the bulk epoxy. The polyester molecules acted as a plasticizer for the epoxy resin when the polyester was added in low amounts. This increased the bulk fracture toughness of the epoxy resin by 30%. Polyester modified glass/epoxy laminates were produced and tested for Mode I interlaminar fracture toughness and flexural properties. The increased toughness of the epoxy matrix led to a 60% increased Mode I interlaminar fracture toughness of the laminates, without negatively affecting flexural stiffness and strength of the laminates.     

Effects of curing time and temperature on strength development of inorganic polymeric binder based on natural pozzolan

This paper reports the results of a study on the influence of curing conditions on compressive strength development in inorganic polymeric binder prepared from natural pozzolan. Three mixes with different chemical formulations were prepared and cured hydrothermally at different temperatures and times. In particular, the effect of a precuring at an atmosphere of more than 95% relative humidity at room temperature on compressive strength development before the application of heat was studied. Different curing regimes including hydrothermal treatment in steam-saturated atmosphere at different temperatures of 45, 65, 85 °C and for different time periods of 5, 10, 15, and 20 h after 1 and 7 days of precuring were applied. The mix exhibiting the maximum compressive strength after hydrothermal treatment was selected and cured in autoclave at temperatures of 125, 150, 180, and 210 °C for different time periods of 20, 30, 40, and 50 h for investigating the effects of higher times and temperatures of curing on strength development and also to determine the maximum achievable compressive strength. Results show that relatively long precuring in humid atmosphere is very beneficial for compressive strength development. The highest compressive strength achieved for three different regimes of curing including 28 days at an atmosphere of more than 95% relative humidity at 25 °C, 20 h hydrothermal treatment at 85 °C after 1 day precuring, and 20 h hydrothermal treatment at 85 °C after 7 days precuring were 37.5, 37.5, and 57.5 MPa, respectively. The maximum achievable compressive strength under autoclave curing at 210 °C for 30 h after 7 days of precuring was 108.7 MPa.     

Effects of activator type/concentration and curing temperature on alkali-activated binder based on copper mine tailings

This article investigates the effects of activator type/concentration and curing temperature on alkali-activated binder based on copper mine tailings (MT). Different alkaline activators including sodium hydroxide (NaOH), sodium silicate (SS), and sodium aluminate (SA) at different compositions and concentrations were used and four different curing temperatures, 60, 75, 90, and 120?°C, were considered. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), and X-ray diffraction (XRD) were conducted to investigate the effect of these factors on the unconfined compressive strength (UCS), microstructure, and phase composition of the binder. The results indicate that NaOH concentration and curing temperature are two important factors that affect the UCS and micro-structural properties of the alkali-activated MT binder. The optimum curing temperature, i.e., the curing temperature at the maximum UCS, depends on the NaOH concentration, lower optimum curing temperature at smaller NaOH concentration. Addition of aqueous SS to the NaOH solution can lead to strength improvement, with the highest UCS obtained at a SiO₂/Na₂O ratio of 1.0–1.26. Addition of powder SA to the NaOH solution profoundly delays the setting at 60?°C but improves the UCS at 90?°C. The SEM/EDX results show highly heterogeneous microstructure for the alkali-activated MT binder as evidenced by the variable Si/Al ratios in different phases. The XRD patterns indicate a newly formed crystalline phase, zeolite, in the 90?°C-cured specimens. The results of this study provide useful information for recycling and utilization of copper MT as construction material through the geopolymerization technology.     

Composite carbon paste biosensor for phenolic derivatives based on in situ electrogenerated polypyrrole binder

Amperometric biosensors based on new composite carbon paste (CPE) electrodes have been designed for the determination of phenolic compounds. The composite CPEs were prepared by in situ generation of polypyrrole (PPy) within a paste containing the enzyme polyphenol oxidase (PPO). The best paste composition (enzyme/pyrrole monomer/carbon particles/Nujol) was determined for a model enzyme, glucose oxidase, according to the enzymatic activity of the resulting electrodes and to the enzyme leakage from the paste during storage in phosphate buffer. The in situ electrogenerated PPy enables improvement in enzyme immobilization within the paste since practically no enzyme was lost in solution after 72 h of immersion. Moreover, the enzyme activity remains particularly stable under storage since the biocomposite structure maintains 80% of its activity after 1-month storage. Following the optimization of the paste composition, PPO-based carbon paste biosensors were prepared and presented excellent analytical properties toward catechol detection with a sensitivity of 4.7 A M(-1) cm(-2) and a response time lower than 20 s. The resulting biosensors were finally applied to the determination of epicatechin and ferulic acid as flavonol and polyphenol model, respectively.     

Transparent conductive thin film synthesis based on single-walled carbon nanotubes dispersion containing polymethylmethacrylate binder

Transparent conductive hybrid thin films of single-walled carbon nanotubes (SWNTs) and polymethyl methacrylate (PMMA) are fabricated using dispersions containing SWNTs and water-borne PMMA binder. The polymer binder was used as adhesion promoter between the SWNTs and the substrate. The polymer binder content in the SWNTs dispersion is varied to obtain the optimum optical transmittance, electrical conductivity, and mechanical adhesion. The PMMA and SWNT network formed the composite over substrate. The fabricated SWNTs/PMMA hybrid films are immersed in nitric acid (HNO3) and thionyl chloride (SOCl2) to improve electrical conductivity. SWNTs films with 0.2-0.6 mg/ml polymer binder have sheet resistance of 80-140 ohms/sq at a transmittance of about 80% and a strong adhesion on glass substrate. Furthermore, the electrical stability of the films is improved via the PMMA addition. This results indicates that the SWNTs/PMMA hybrid films fabricated by this method can be used as an alternative of indium tin oxide (ITO) film on flexible substrate.     

Copper thin-film temperature-sensitive elements,resistive thermal transducers,and thermometers based on them

We consider the characteristic features of domestic copper temperature-sensitive elements fabricated on the basis of modern thin-film technology, and also thermal transducers and resistance thermometers with thin-film temperature-sensitive elements.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 45–47, August, 1995.