Special Binders Research Articles

Production of Permanent Magnets from Recycled NdFeB Powder with Powder Extrusion Moulding

In the last fifteen years, several groups have investigated metal injection moulding (MIM) of NdFeB powder to produce isotropic or anisotropic rare earth magnets of greater geometric complexity than that achieved by the conventional pressing and sintering approach. However, due to the powder’s high affinity for oxygen and carbon uptake, sufficient remanence and coercivity remains difficult. This article presents a novel approach to producing NdFeB magnets from recycled material using Powder Extrusion Moulding (PEM) in a continuous process. The process route uses powder obtained from recycling rare earth magnets through Hydrogen Processing of Magnetic Scrap (HPMS). This article presents the results of tailored powder processing, the production of mouldable feedstock based on a special binder system, and moulding with PEM to produce green and sintered parts. The magnetic properties and microstructures of debinded and sintered samples are presented and discussed, focusing on the influence of filling ratio and challenging processing conditions on interstitial content as well as density and magnetic properties.

Nano-Si Filled Graphite Anode Particles by Mechanofusion

Silicon-graphite composite anode materials for Li-ion cells were synthesized by embedding nano-Si into voids within natural graphite by mechanofusion, followed by carbon coating by chemical vapor deposition. In the resulting structure, voids within the natural graphite were completely filled with silicon nanoparticles encapsulated in carbon. This resulted in the silicon being protected from reaction with the electrolyte. The as-prepared silicon-graphite composites were shown to cycle well in electrodes with no special binders (PVDF) and in conventional electrolytes without any additives (i.e. no fluoroethylene carbonate). Furthermore, nearly all the Si within the voids were fully active. This provides a promising and simple strategy for silicon-graphite composites that can be used as a drop-in replacement for graphite to increase Li-ion cell capacity.

Effect of Variable Synthesis Conditions on the Formation of Ye'elimite-Aluminate-Calcium (YAC) Cement and Its Hydration in the Presence of Portland Cement (OPC) and Several Accessory Additives.

In the presented study, ye'elimite-aluminate-calcium (YAC) cement was synthesized. Complete synthesis of crystalline phases was achieved at a temperature of 1300 °C, which is 150 °C lower than the temperature standardly used in the processes of obtaining calcium aluminate cements (CAC). The greatest amount of ye'elimite phase (Klein complex), roughly 87% by mass, was acquired utilizing a sulphur ion transporter derived from artificial dihydrate gypsum obtained in the flue gas desulphurization process (variation I). In the case of anhydrite, the amount of synthesized crystalline ye'elimite in the clinker was 67% by weight (variant II). Depending on the synthesis conditions in the clinkers, the quantity of obtained calcium aluminates (C12A7, CA, and CA2) ranged from 20 to 40% by weight. Studies on the hydration process of YAC cement samples showed that the main products are hydrated calcium aluminates and dodecahydrate calcium alumino-sulphate. In sinters of YAC and OPC, no crystalline ettringite was observed. Hydration analysis of Chinese cement revealed the presence of crystalline ettringite and dodecahydrate calcium alumino-sulphate, as well as hydrated calcium silicates of the CSH type accompanied with pseudo-crystalline Al(OH)3. The obtained clinkers from variants I and II constitute a special binder, which, due to its phase composition after hydration, can be used in the construction of reactors for biogas production in eco-energy applications.

Functional assignment of technological accessories for woodworking

Forming a heat and sound insulation board from wood using non-combustible binders can increase the fire protection of the material by forming a protective layer of coke. This will make it possible to develop a new type of fireproof roofing products for building structures. It is not always advisable to treat the surface of a heat and sound insulation board with fireproof coatings, since after prolonged thermal exposure, the combustion stage can be transferred to the interior of the material by smoldering. Therefore, the manufacture of fire-resistant heat- and sound-insulating wood materials, the study of fire protection and the impact of their components on this process is an unresolved component of ensuring the fire resistance of building structures. And, accordingly, they determine the need for such research.
 The paper presents the results of research into the process of protecting wood wool boards with binders based on fire-resistant coatings. Tests on model samples of a wooden board showed that the material based on wood wool and an inorganic binder is characterized by heat absorption and inhibition of oxidation in the gas and condensed phase and the formation of a thermally protective ceramic layer on the surface of the wood. Experimental studies have confirmed that a material based on wood wool and an inorganic binder at a ratio of 1:1 refers to combustible materials, since its smoldering was recorded during exposure to temperature. So, by thermal action for 90 s, the material ignited and the flame spread over the first three zones for 41 s. On the other hand, an increase in the amount of an inorganic-based binder and the use of an organic-mineral binder does not lead to a material fire. In this case, the maximum temperature of the flue gases was about 120 °C, and the flammability index was 0 due to the decomposition of fire retardants under the influence of temperature with the release of incombustible gases, which inhibit the oxidation of the material and significantly increase the formation of a heat-protective layer of coke on the surface of the material. This leads to inhibition of heat transfer of the high-temperature flame to the material. Due to this, it became possible to determine the conditions of fire resistance of the material by forming a barrier for thermal conductivity. The obtained results indicate the possibility of targeted regulation of high temperature transfer processes to organic material by using special binders for wood products.

ПОЛУЧЕНИЕ СМЕШАННЫХ КОМПОЗИЦИОННЫХ ЦЕМЕНТОВ НА ОСНОВЕ ФЕРРИТНОГО КЛИНКЕРА

The possibility of using ferritic clinker as a component of binders with special performance properties is considered. Such types of cements can solve the problems of providing the construction industry with high-strength, resistant to external aggressive effects and relatively cheap binders. However, the mechanism of hardening and curing of cement stone obtained by using ferritic clinkers is complicated and depends on a number of parameters.
 It was found that the greatest thermal effect (more than 70%) during the hydration of the resulting ferritic clinker with the introduction of various additives (lime and gypsum stone) is achieved up to 4 hours from the moment the binder compositions are mixed by means of a calorimetric analysis carried out during the hydration of the developed special binder compositions. That corresponds to the course of the induction period of hydration of the used Portland cement, at the time of the occurrence of primary contacts between crystalline hydrates and sufficient mobility of the cement mass. In this time interval, the strength of the cement stone is not high enough and the produced iron-containing hydration products are able to fill the space of the cement matrix, making it more dense and less defective. 
 The formation of iron-containing crystalline hydrates from ferritic clinker can proceed in several stages: hydrolysis of dicalcium ferrite at the initial stage of the reaction and further interaction of its products with portlandite in the period from 7 to 14 days from the moment of mixing the binder compositions. The main crystalline hydrates formed from ferritic clinker are iron-bearing ettringite and hydrogarnet.
 The study of the physical and mechanical characteristics of cement stone showed that the optimal content of ferritic clinker in the composition of the binder compositions is 5%. With a given quantity, the strength of the cement stone in compression and bending exceeds that of the control sample by 11.5%. The input of 15 and 30% ferritic clinkers into the composition of special binders reduces the strength characteristics by 15-20%.

National Exposure Classes of Concrete in Hungary

Sufficient durability of concrete and reinforced concrete structures is always required, mainly if it is exposed to extraordinary (severe) environmental attack - much over the well-known classes in European Standard for Concrete EN 206. In this case, appropriate concrete composition (e.g. special binders, etc.), strength, low porosity and sufficient concrete cover are required to withstand these special environmental exposures. The present paper deals with the additional exposure classes for these severe cases added to the Hungarian Standard MSZ 4798, which is the national version of EN 206. Maybe CEN could also use and add some of these “X-new” classes in the following version of the standard EN 206.

REFINEMENT OF THE FOUR-COMPONENT SYSTEM MgO – CaO – Al2O3 – Cr2O3 SUB-SOLIDUS STRUCTURE INCLUDING THE Сa6Al4Cr2O15 COMPOUND

The results of theoretical calculations of the subsolidus structure of the four-component system MgO – CaO – Al2O3 – Cr2O3 are presented, taking into account the three-component compound Сa6Al4Cr2O15. Thermodynamic and geometric topological analysis methods were used to establish stable conodes in the specified system. When dividing the concentration tetrahedron MgO – CaO – Al2O3 – Cr2O3 into elementary ones with the involvement of a geometro-topological analysis, it is possible to make an unambiguous closure to the elementary tetrahedron of faces with incident edges (connodes) through a common vertex. The use of this method allows to minimize the number of necessary thermodynamic calculations. The tetrahedra of the MgO – CaO – Al2O3 – Cr2O3 system, taking into account the stable phases, is caused by the presence of three "internal" conodes passing through the three-dimensional space of the concentration tetrahedron: Сa6Al4Cr2O15 – MgO; MgCa3Al4O10 – CaCr2O4, CaCr2O4 – MgAl2O4, which determine the presence of 14 elementary tetrahedra in the subsolidus region. The lengths of conodes and volumes of elementary tetrahedra were calculated taking into account barycentric coordinates and elements of Euclidean geometry. The phases included in the composition of the tetrahedron with the largest relative volume and the smallest asymmetry CaCr2O4 – СaAl2O4 –MgAl2O4 – MgO (185.6 ‰ and 2.55, respectively) have the highest probability of existence in the system, which will allow the development of a sustainable technology for creating composite materials based on calcium aluminochromite cement, with periclase as an aggregate, without special techniques dosage of initial components. At the same time, in the event of a violation of the technological process, magnesium aluminate spinel will be synthesized in the composition of the unformed material, which will not lead to deterioration of the performance characteristics of the composite used. It should be noted that elementary tetrahedra with a high degree of asymmetry, which require appropriate dosage accuracy when predicting the phase composition of synthesized composite materials, are located in areas of the system that are not technologically advantageous from the point of view of obtaining unformed refractories based on special binder materials, and are interest for materials scientists in the ceramic and refractory industries.

Binders for impregnation of fibrous fillers in the production of prepregs

The article presents a review of the scientific and technical information from Russian and foreign periodicals, patents for inventions in the field of using various materials for the production of prepregs. Data on global manufacturers and applied technologies are provided. Prepreg is a polymer composite material based on carbon or glass fabrics. The technology for its production consists in impregnating the reinforcing material with a special binder. Typically, it is the resin in an uncured or partially cured state. Particular attention to polymer composite materials based on glass fibers is paid. The binder is a solution of organic substances, which is used as an impregnating agent. The combination of fibrous fillers and impregnating composition makes it easy to shape the final product. It is showed that the main areas of prepreg applications are the automotive industry, construction, transport, sports equipment, as well as various sectors of the national economyThe composite materials are shown to have a number of advantages, including economic ones. According to the conducted scientific and patent search, the most common components of polymer composite materials are epoxy resin and various types of hardeners.

Statistically Quantifying the Uncertainty in Strength of Marine Clay Stabilized by a Type of Portland‐Fly Ash Cement

This study deals with the variation in strength of clays stabilized by a special binder—the CEM II/B‐V type of Portland‐fly ash cement. Two sources of uncertainties were examined, that is, the uncertainty in cement fraction in the binder, and the nonuniformity in binder concentration resulted from the process of mixing binder slurry with in situ clays. These two uncertainties were quantitatively described as two random variables, and the analyses were conducted through the Monte Carlo simulation method. Results indicate that the strength is insensitive to the cement fraction in the binder but is sensitive to the binder concentration; the variation of the latter even results in an amplified variation of strength. The variation of binder concentration is proposed to be linked up with the variation of strength through the operational parameter of blade rotation number. By doing so, the results could benefit designers in quality control prior to the construction of soil stabilization.

Research on influencing factors of high temperature performance of new type noise reduction micro-surfacing

The micro-surfacing has received widespread attention with its excellent anti-skid performance, waterproof performance, construction characteristics and significant cost advantages. However, the problem of the conventional micro surfacing high driving noise has been criticized. The new noise reduction micro-surfacing has appeared to greatly reduce the traffic noise to a considerable extent and solve the main bottleneck of the further promotion to the micro-surfacing. The noise reduction micro-surfacing proposed in this study has a special binder and gradation, as well as a specific rubber powder filler. Guided by the change rate of the wheel rut width, focused on the four key variables of oil-stone ratio, cement, mineral powder and rubber powder content, the high-temperature performance of the noise reduction micro-surfacing mixture is studied. The research shows: based on the special noise reduction gradation proposed in this article, in order to obtain a new type of noise reduction micro-surfacing with the best anti-rutting performance, the best oil-stone ratio is 10.5%, the best cement content is 1%, and the rubber powder should not exceed 2%.

Study of Eco-Friendly Belite-Calcium Sulfoaluminate Cements Obtained from Special Wastes

Belite-calcium sulfoaluminate (BCSA) cements are special binders obtained from non-Portland clinkers; they have become increasingly more important due to their environmental impact during the manufacturing process compared to Portland cements, such as lower energy consumption and CO2 emissions. The aim of this paper was to assess the possible use of titanogypsum (T) and water potabilization sludge (W) to reduce the amount of natural raw materials (natural gypsum and clay, respectively) used in the production of BCSA cements. Three BCSA clinker generating raw mixes, containing T and/or W, and a reference mix based only on natural materials (limestone, clay, bauxite and natural gypsum) were heated in an electric furnace at temperatures ranging from 1200 to 1350 °C. Quantitative X-ray diffraction (XRD) analysis of the burnt products showed high conversion of reactants towards the main hydraulically active BCSA clinkers components (C2S and C4A3$), particularly at temperatures of 1300 and 1350 °C. Isothermal calorimetric measurements, differential thermal–thermogravimetric and XRD analyses as well as porosimetric measurements showed that all BCSA cements, from mixing the clinkers (at optimum temperatures) with commercial anhydrite, exhibited similar hydration behavior.

Influence of different types of chamot on a structure and properties of porous ceramics

The results of research of porous materials on the basis of products of ceramic production - chamot as a fractionating filler are given.. The features of formation of structure of material at the use of chamot with different chemical and mineralogical compositions in the conditions of speed baking are shown.
 Porous ceramics for filtration and aeration is obtained by a technology based on the regulation of porosity parameters by the use of chamotte of a certain granulometric composition and special binders.
 However, the granulometric composition of chamotte is a necessary but not sufficient factor to optimize the properties of porous filter ceramics. Along with the granulometry of chamotte, its chemical and mineralogical composition and surface energy must be taken into account. It depends in turn on the technological properties and the firing parameters of the original clay raw material.
 This paper presents the results of a study of porous materials based on ceramic products - chamotte as a fractionated filler. The chemical and mineralogical composition of chamotte made of poly-mineral clay at maximum firing temperature of 950°С and of refractory clay at firing at 1320°C was analyzed.
 The energy state of the surface of the chamotte particles was determined with the wetting by polar and non-polar liquids (water and benzene respectively). The differences in the specific effective surface area, lyophilicity and filtration coefficients was determined.
 The peculiarities of the formation of the pore structure of ceramics obtained using the specified samples of chamotte in the conditions of high-speed firing in the roller oven are shown. Significant differences in the formation of open and closed pores were observed, the predominant specific proportion of open pores in the material using polymineral clay.
 The possibility of properties regulation of the pore structure and the energy state of the surface of the filter material when applying a mixture of chamotte varieties was experimentally confirmed.

Special Issue Low Binder Concrete and Mortars

It is well known that, after water, concrete and mortars are the most demanded materials worldwide [...]

Application experience of composite external reinforcement systems and optical monitoring of building structures

This article describes results of the widespread use of external reinforcement systems for reinforced concrete and metal man-made structures based on domestic and foreign polymer composite materials (PCM), as well as fiber-optic monitoring systems, including a network of fiber-optic sensors (FOS) and a hardware-software complex that track the actual state of the control object throughout the entire life cycle. It is shown that for reinforced concrete structures it is advisable to use composite systems of external reinforcement installed directly on the reinforcement object by contact molding using special cold curing binders. In relation to metal structures, this technology is unacceptable due to a significant difference in the coefficients of linear thermal expansion of the metal and the carbon composite. To solve this problem, reinforcement technology has been proposed, which consists in installing discrete mechanical fasteners of finished composite spigots (similar to metal ones) made by autoclave and autoclave-free molding methods. In the event that deviations from the normative indicators for this type of structures are detected, the necessary set of measures is taken to strengthen, after which the monitoring system carries out a similar control, the results of which characterize the quality of the work performed. Thus, the monitoring system can act both as an effective tool for structural control and carry out local time monitoring before or after the relevant works on strengthening and reconstruction, and in real time work throughout the entire period of operation.

СТЕНОВЫЕ СИЛИКАТНЫЕ МАТЕРИАЛЫ НЕАВТОКЛАВНОГО ТВЕРДЕНИЯ С ПРИМЕНЕНИЕМ КРЕМНЕЗЕМИСТОГО СЫРЬЯ И АЛЮМОСИЛИКАТНОГО ВЯЖУЩЕГО НА ОСНОВЕ НЕТРАДИЦИОННЫХ ГЛИНИСТЫХ ПОРОД

Among the used building materials, structural autoclave silicate products occupy one of the leading places. The traditional technology of silicate materials uses autoclave processing of products, the main disadvantage of which is the high energy intensity. In order to create non-autoclave silicate composites based on conventional siliceous raw materials, it is proposed to use a special aluminosilicate binder based on clay rocks of the incomplete stage of mineral formation of a certain genesis and quicklime. The strength of silicate materials is growing as a result of the neoplasm process. They are synthesized in the chemical reaction of quicklime with components of clay rocks when using high pressure and temperature modes in an autoclave, and when steaming with temperatures up to 100 °C. The high specific surface of the aluminosilicate binder provides an increase in the packing density of the material. Due to the structural features of the CaO-SiO2 (Al2O3)-H2O system based on unconventional clay rocks, the process of formation of the microstructure of the material, which continues and after hydrothermal treatment of the products, gives the material hydraulic properties. The proposed binders and their production technologies can be implemented in small and medium-sized businesses, which will allow to obtain competitive non-autoclave silicate materials with a compressive strength of up to 25 MPa and an average density of 1850 kg/m3.

The Effectiveness of Sustainable Construction Materials by Using U-Shaped Composite Spacer Block (UCop)​

Nowadays in construction development, the needs of construction materials that have a unique reinforced concrete design with good quality, reasonable market price, and easy installation techniques has been prioritized. Therefore, this study aimed to produce an alternative new construction material that can fulfill the requirements. The U-shaped composite spacer block (UCop) through the production of Cement Bonded Particle Board (CBPB) as a specimen block was produced from the wood waste of carpentry work combined with Shorea spp. (Seraya red and white) particle size approximately 0.4mm - 2.00 mm. Then it was mixed together with Portland cement by using a ratio 1:2.5. The mixture was then added with Ammonia Chloride (Al2SO4) and Calcium Chloride (CaCl2) act as additives for this product. The physical and mechanical tests were conducted in this study. The results were showed that the thickness expansion was achieved an average of 1.79 %, which was passed the minimum requirement of MS934:1986 standards. However, the flexural strength did not meet the minimum standards. The poor mixing technique was attributed to the results. However, UCop still could contribute as an alternative solution in ease the concrete pouring process using a special binder, giving the spacer block any resistance to formwork of columns or beams is filled with concrete. The high-impact innovations of this product in construction such as it can help the process to be more efficient and to reduce construction costs, next indirectly preserve the nature.

Experimental studies to determine the physico-mechanical characteristics of soils improved with special hydraulic binders

The complexity of the construction works and site conditions, combined with environmental factors, led to the necessity of using special mineral binders with physical and chemical properties superior to the usual binders. Taking into account the above arguments, the paper presents the results of experimental laboratory studies in order to determine the physical and mechanical characteristics of soil used for a road embankment, after improvement with a special lime-based hydraulic binder. Since improvement recipes vary from one soil to another, it is important to always determine the characteristics after treatment. Also, the method of mixing the binder and soil decisively determines subsequent performance. As part of a larger study aiming at assessing the various factors of influence on the treated soil characteristics, two comparative studies were carried out, each consisting in the recipe formulation using 3 different binder ratios, the difference being given by the parameters used for specimen compaction: normal or modified Proctor test. The study followed the influence of the mechanical compaction work on the mechanical behaviour of the specimens over time after different times of curing.

Powder injection molding of complex-shaped aluminium nitride ceramic with high thermal conductivity

Aluminum nitride (AlN) is a promising material for heat sinks and microelectronic applications because of the advantages of high theoretical thermal conductivity, high mechanical strength, good electrical insulation, low dielectric constant and low thermal expansion coefficient. However, the difficulties in shaping complex-shaped parts with a high thermal conductivity have retarded the wide applications of AlN ceramic. Herein, we design a new binder system containing resin components and adopt the powder injection molding technology to fabricate complex-shaped AlN parts. After the debinding process, the special binder system would produce residual carbon, which could react with Al2O3 and result in decreasing oxygen impurity and forming the yttrium-rich aluminates. The yttrium-rich aluminates can accelerate the densification of AlN ceramic and fasten the oxygen on the triangular grain boundary, leaving the clean grain boundary beneficial for high thermal conductivity. The as-prepared AlN parts with complex shape possess a high thermal conductivity of 248 W m−1 K−1.

Additive manufacturing of ammonium perchlorate composite propellant with high solids loadings

The effective solid propellant burning rate in a rocket depends on surface area and propellant composition. Currently, the surface area geometry in a rocket is limited to what can be practically cast using molds, etc. Additive manufacturing (AM) could allow the production of unique propellant grain geometries, however printing propellants with high solids loadings and viscosities is not readily possible using currently available printers. A new AM direct write system developed recently in our laboratory, is capable of printing visibly low-void propellants with high end mix viscosities into highly resolved geometries. The system was used to print ammonium perchlorate (AP) composite propellants at 85% solids loading using hydroxyl-terminated polybutadiene (HTPB) and a UV-curable polyurethane binder. The change in HTPB propellant viscosity with time after mixing was measured and the microstructure of the strands was evaluated with X-ray tomography scans. The burning rate of printed and cast strands was measured to compare the quality of the strands at high pressure, since propellants with significant voids should catastrophically fail due to flame spreading. The printed samples burned in a planar fashion up to pressures of 10.34 MPa with consistent rates that were comparable to the cast propellants. The HTPB propellant used was not optimized and showed some porosity due to gas generation, but strands printed with the UV binder exhibited extremely low porosity. A strand printed with no gaps in one half and gaps in the other failed catastrophically where intended at high pressure, demonstrating the ability to spatially grade propellants. This new system can produce adequate strands of composite propellant with high solids loadings without the addition of solvents, special binders (low viscosity, thermal softening, etc.), or restricting use to formulations with lower viscosities, and enables the fabrication of complex propellant grain geometries.

3D printing of biodegradable parts using renewable biobased materials

The paper presents ways of utilising the additive manufacturing process 3D-printing using renewable biobased materials, with a focus on adapted packaging for sensitive components. This application provides an attractive scenario for sustainable production and the re- or upcycling of waste material such as wood flour, rice husk or miscanthus fibre. Packaging of prototypes with sensitive or filigree structures or made of fragile materials is currently difficult, because standardized packages are often not suitable and cost for adapted packages are high. Within this study, CAD-data based adapted packaging made of renewable raw materials is addressed. The 3D-printing process was modified for using conditioned biobased fibre and a special binder. Furthermore, a software tool was developed to create adapted packaging designs by using the individual part geometry.In this way and in combination with AM processes, sustainable and biodegradable packaging for complex components can be generated within a short time. The manufactured packaging is conform to the demands of packaging for fragile goods and can be produced just-in-time.