Bending Strength Of Samples Research Articles

Mechanical Properties and Corrosion Resistance of Hot-Pressed Dysprosium Molybdate Samples

The purpose of this work was to study the consolidation features using hot pressing method of dysprosium molybdate billets and to study their mechanical properties and corrosion resistance.Methods. The technological and physical properties of the mechanosynthesised dysprosium molybdate powder were investigated. Properties and structure of the obtained dysprosium molybdate powder were studied by methods of chemical and X-ray phase analyses and scanning electron microscopy. Bulk density of dysprosium molybdate powder was studied according to GOST 19440-94. Flowability of dysprosium molybdate powder was determined according to GOST 20899-75. The specific surface of dysprosium molybdate was determined using a specific surface analyser NOVA 1200e (USA) by the method of low-temperature nitrogen adsorption (BET). X-ray phase analysis of mechanosynthesised dysprosium molybdate powder was carried out on a diffractometerResults. The bending strength of hot-pressed dysprosium molybdate specimens was determined, it was found that the highest value of the bending strength was recorded for these specimens at a pressing pressure of 35 MPa and is 314 MPa. The corrosion resistance of hot-pressed dysprosium molybdate samples in aqueous coolant at a temperature of 100 °C was studied. It was recorded that the mass of the mechanosynthesised dysprosium molybdate specimens remained practically unchanged throughout the corrosion resistance test in aqueous coolant.Conclusion. Tests on corrosion resistance have shown absence of change of mass of samples from dysprosium molybdate during 60 hours. The bending strength of samples from dysprosium molybdate obtained by hot pressing at pressure 35 Pa, temperature 1400 oÑ and time of holding under pressure 5 min is 314 MPa.

Влияние полипропиленового волокна на цементный закладочный композит на основе хвостов обогащения

Introduction. The advantages of technology with backfill in minerals extraction predetermined their widespread use despite the high cost of production. One of the ways to reduce the backfilling cost is the use of tailings. However, earlier studies did not consider the inhomogeneity of shapes, sizes and internal mutual arrangement of particles, as well as the inhomogeneity of phases and density, which is characterized by the presence of pores. Materials and methods. Comparative analysis of samples with different recipes was used to investigate the bending strength of polypropylene fiber-reinforced backfill. A high-frequency automatic laboratory setup with strength transducers (load cells) was used to measure the bending characteristics. Optical moving digital image correlation (3D-DIC) method was used to track and automatically store the obtained results. Microstructure of the prepared and cured backfill was studied to correlate the obtained values. Results. 1. Maximum bending strength was demonstrated by unreinforced samples with 1:4 cement/tailings combination compared to the rest of samples regardless of the presence or absence of reinforcing fiber in the composition; 2. Directly proportional dependence between the increase in bending strength of samples and increase in the cement/ tailings ratio in backfill was established; 3. Increase in bending strength of the samples is maximum at low cement/tailings ratio in backfill composite; 4. There is a linear increase in peak strength and deflection values as the cement/tailings ratio in reinforced backfill increases. Discussion. Compaction of the internal structure is observed when reinforcing the composite with polypropylene fiber. It is noticeable that the compaction occurs due to fiber bonding, which allows improving the bending characteristics of samples. Such compaction is observed in all the investigated reinforced composites with ratios of 1:4, 1:6, 1:8. In some cases a decrease in fiber diameter is observed, which can be explained by the factor of occurrence of yanking or torsional forces at the moment of fracture. All the changes in reinforcing fibers confirm the fact that they are prone to deformations. Conclusion. The following conclusions can be drawn from the research conducted: 1. Unreinforced samples with a cement/tailings combination of 1:4 have the maximum bending strength in comparison with other samples, regardless of the presence or absence of reinforcing fiber in the composition; 2. Reinforcement of backfill with polypropylene fiber changes the fracture behavior of samples and passes from brittle to ductile at maximum strain rate; 3. Reinforcing fibers in the cement backfill have an overlapping effect, which significantly slows the development of cracks and increases the ductility of the material. Resume. The results of the research can be useful in the creation of high-strength and resistant to increased bending stresses artificial mass where tailings are used as an aggregate. In the future there is a need to study the cement backfill with different types of reinforcing fibers.

Prospects of using the polymetallic ore processing waist for producing hardening mixtures

Purpose. Justification of possibility to create the hardening mixtures with filler based on tailings of the Akshatau mining and processing complex for strengthening the quarry benches, inter-chamber pillars and excavation roofs and producing building materials. Methodology. The complex approach is applied including experimental methods of physical and chemical and mechanical analysis of the phase composition and properties of ore processing wastes. The practicability of using the tailings of polymetallic ore processing as an inert filling of hardening mixtures is estimated; the compressive and bending strength of samples is determined after the mixture solidification as well. Findings. Based on X-ray phase analyses, differential thermal and chemical analyses, the ore tailings composition was determined. The optimal qualitative composition of the hardening mixture with specified rheological and strength properties, as well as the technological mode of its preparation, have been determined. Originality. The peculiarities of hydration processes in the cement-water-limestone system are clarified and a new formulation of a hardening mixture with specified rheological and strength properties have been developed. Practical value. The proposed composition of hardening mixtures with filler based on ore processing waste is aimed at strengthening the fractured area of the rock mass. This increases the stability of rock openings and provides safety of mining. The involvement of ore processing waste in the production of hardening mixtures and other building materials is a positive solution in terms of the disposal of these wastes. Reducing the amount of accumulated waste contributes to minimizing environmental risks in mining regions. The obtained results are significant for the construction industry. They provide the expansion and reproduction of the raw material base through using the waste of processing the ore of Akzhal deposit.

Alkali-treated wheat gluten cross-linked with sodium alginate as a bio-based wood adhesive for interior grade particleboard

A bio-based wood adhesive formulation free of formaldehyde and made from alkali-treated wheat gluten (WG) and sodium alginate (SA) was developed. Its formulation was optimised, and it was characterised by Fourier Transform Infrared (FT-IR) spectroscopy. The bio-adhesive was utilized to make particleboards both with virgin wood particles and recycled wood particles. A dry bio-adhesive content of 35% (w/w) was used to make samples with both type of particles. Single-layer samples of 10 mm thickness were obtained using wood particles of 1 mm (both virgin and recycled). These samples then were subjected to 3-point bending tests. Whereas the bending strength of samples made with recycled wood particles was 18.09 N/m2 and therefore satisfied Type 18 of the Japanese industrial standards (JIS A 5908:2015), the bending strength of the samples made with virgin wood particles was 8.08 N/m2 and satisfied ‘Type 8 Base particleboard Decorative particleboard’ of the Japanese standards. The density of particleboard samples made from recycled wood particles was 916 kg/m3, while that of samples made from virgin wood particles was 732 kg/m3. The alkali-treated WG and SA bio-adhesive has the potential to be used to re-manufacture particleboards, which can then be recycled and not disposed in landfills.

Fabrication and characterization of porous mullite ceramics with ultra-low shrinkage and high porosity via sol-gel and solid state reaction methods

Porous mullite ceramics with ultra-low shrinkage and high porosity were prepared by solid state reaction between MoO3 and mullite precursor powders which were synthesized from tetraethylorthosilicate and aluminium nitrate nonahydrate via sol-gel methods. The synthetic process of mullite precursor powder and effects of MoO3 amount on the phase composition, microstructure, physical properties such as firing shrinkage, open porosity, bending strength, water absorption and bulk density of porous mullite ceramics were investigated. The results indicated that the addition of MoO3 not only lowered the mullite forming temperature from 985.4 to 853.3 °C, but also restrained densification behavior of samples due to the formation of mullite and Al2O3–MoO3 solid solution, besides, MoO3 also improves the formability, open porosity and bending strength of samples. The optimal amounts of MoO3 is 8 wt%, and the resultant samples exhibit outstanding properties, including a low shrinkage rate of 1.86 ± 0.07%, an open porosity of 61.91 ± 0.16% and a bending strength of 9.35 ± 1.11 MPa.

Effect of PyC interface phase on the cyclic ablation resistance and flexural properties of two-dimensional Cf/HfC composites

Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface.

Фазовый состав, структура и некоторые свойства материалов на основе ВКВС боксита композиционного состава в системе Al2O3 – SiO2 – SiC

The effect of temperature and duration of heat treatment of samples based on a highly concentrated ceramic binder suspension (HCBS) of a composite composition (bauxite + 11% VDKS), as well as with an additional content of 15% silicon carbide on their phase composition, structure, and some properties is studied. Long-term heat treatment (60 and 120 hours) in the temperature range 1300 - 1400 ° C is carried out in a tunnel kiln for firing dinas. In the process of heat treatment, the process of formation of secondary mullite, the oxidation of SiC followed by mullite formation, proceeds. The influence of the heat treatment duration on the phase composition, as well as the strength, apparent density, growth, SIC oxidation state, and bending strength of samples containing 15% SiC are characterized. It is found that the minimum porosity value (2.7 %) is observed when the heat treatment duration is 8 hours. This drop in porosity and a slight decrease in density is due to a certain degree of mullitization or SiC oxidation, but also to the formation of a significant volume of closed porosity. With increasing the duration of the firing process to 60 and 120 hours, the porosity indicators increase significantly, and the density decreases sharply.

Anisotropic electromechanical properties of GaN ceramics caused by polarisation

Based on three-point bending tests and finite element modelling, effects of polarisation directions are investigated on the mechanical and electrical properties of GaN piezoelectric semiconductor ceramics (PSCs). It is shown that polarisation leads to anisotropic electromechanical properties of PSCs. For GaN samples polarised along the vertical direction, their conductive capabilities enhance by nearly 50%, and however, there are almost no changes in ones with horizontal polarisation. Bending strengths of samples with vertical polarisation increase by 11.6% because piezoelectric charges are driven along the polarisation direction under mechanical loading. It is the correlation between mobility and polarisation direction that largely affects the fracture toughness of GaN PSCs. These experimental findings indicate that, in contrast to traditional ceramics, the electromechanical properties of GaN ceramics can be tailored through polarisation directions.

Fabrication of SiC bodies by optimized gel-casting method

In this research, acrylate gel maker monomers Mathacrylamide (MAM) and Methylenebisacrylamide (MBAM) were used through a gel casting process to fabricate SiC bodies. Investigation of rheological behavior of suspensions showed that optimum amount of surfactant (Tetramethylammonium hydroxide) was equaled with 0.7 wt% of ceramic powders and ceramic powders could be added up to 37 vol% of solvent without any problems in casting. The effects of monomers content, monomers ratio and also solid loading on gelation time, bending strength of samples were investigated. Results showed that increasing the monomers content (MAM + MBAM) and ceramic solid loading led to the reduction of gelation time. Also alteration of these parameters resulted in variation of samples bending strength from ~6 MPa to 19 MPa, the best strength was obtained in the sample containing 35 wt% monomers with the MAM/MBAM ratio of 3 and 35 vol% SiC. Finally the samples containing different amounts of SiC were casted according to the pre-determined optimum parameters and after being dried they were sintered at 2150 °C for 1 h. According to the results, the highest density, Young's modulus, hardness and indentation fracture resistance were obtained in sample containing 37 vol% SiC and were equaled with 96.89%, 499.24 GPa, 27.51 GPa and 6.3 MPa·m1/2, Respectively. Microstructural studies showed that cleavage fracture planes, crack deflection and branching were the most important mechanisms on toughness enhancement.

Influence of the Matrix Grain Size on the Apparent Density and Bending Strength of Sand Cores

Abstract The results of investigations of the influence of the matrix grain sizes on properties of cores made by the blowing method are presented in the hereby paper. Five kinds of matrices, differing in grain size compositions, determined by the laser diffraction method in the Analysette 22NanoTec device, were applied in investigations. Individual kinds of matrices were used for making core sands in the Cordis technology. From these sands the shaped elements, for determining the apparent density of compacted sands and their bending strength, were made by the blowing method. The shaped elements (cores) were made at shooting pressures being 3, 4 and 5 atn. The bending strength of samples were determined directly after their preparation and after the storing time of 1 hour.

Influence of micron size aluminum particles on the aging properties and wear resistance of epoxy resin coatings

Abstract In this work, an unoxidized aluminum particle/epoxy composite coating was used to cover the surface of pure epoxy resin to reduce the loss of strength after water-heat aging and to improve the wear resistance. The samples were maintained in a water bath at 80°C for 100 days to accelerate the aging process. After water-heat aging, the tensile and bending strengths of the pure epoxy samples were reduced from 30 MPa and 60 MPa, respectively, to 26 MPa and 55 MPa, respectively. However, the tensile and bending strengths of the sample with 6 wt.% aluminum particles were reduced from 39 MPa and 95 MPa to 36 MPa and 89 MPa, respectively. The sample with 6 wt.% aluminum particles exhibited the lowest tensile and bending strength loss rates, 7.2% and 6.1%, respectively, which were 37.4% and 40.8% lower, respectively, than those of the pure epoxy. Additionally, the wear rate and friction coefficient of the samples with 6 wt.% aluminum particles were 2.5×10-6 cm3/min·N and 0.415, respectively, corresponding to a reduction of 35.9% and 30.0%, respectively, compared with the pure epoxy. Thus, it was found that the addition of unoxidized aluminum particles can efficiently increase the water-heat aging resistance and wear resistance of epoxy resin.

Effect of polydimethylsiloxane on the mid-temperature strength of gelcast Al2O3 ceramic parts

An approach using polydimethylsiloxane (PDMS) as mid-temperature strengthening phase in gelcasting for the fabrication of ceramic parts with complex internal cores was firstly proposed and adopted. The bending strength of samples with PDMS at 500°C was greatly improved from almost 0 to 1.037MPa when 4wt.% PDMS was added. The distinct networks formed by PDMS were responsible for the improvement in mid-temperature strength which was confirmed by the result of scanning electron microscopy (SEM). Based on the analysis of X-ray scan, the validity of PDMS was also testified in experiments.

Regeneration and recycling of waste thermosetting plastics based on mechanical thermal coupling fields

In view of the present situation that the recovery of waste thermosetting plastics and products is difficult and the utilization rate is low, regeneration mechanism, regeneration methods and recycling process of waste thermosetting plastics under mechanical thermal coupling fields are proposed. Regeneration powders of Thermosetting Phenolic plastic are obtained by mechanochemical activated regeneration methods, the molecular structure, properties and crosslink density of phenol regeneration materials are analyzed. Analysis results show that network crosslinked molecular structure was destroyed, reactive groups produced and the crosslink density decreased. The activity of regeneration powders was reinforced and its plasticity was also improving, so the utilization rate was improved. Regeneration composite plastics were manufactured by hot press molding or extrusion compression molding. The microstructure of regeneration composite plastics was analyzed, and its mechanical strength was tested. Results showed that the tensile strength and bending strength of samples (weight ratio ≥ 50%) respectively exceed 15.88 MPa and 33.49 MPa. At last process parameters for regeneration effects were discussed, and these parameters were optimized. When particle size was 80 mesh (size ≤ 0.18 mm), quality proportion was 50~70%, pressure was 10Mpa, heating temperature was 180~190°C, the optimal effects for regenerated composite were achieved.

Synthesis of Mullite Using Low-Grade Bauxite and Coal Gangue

The total bauxite reserves of China are about 3.7 billion tons, however the principal and the first-class bauxite reserves account for only about 20%. A large number of coal gangue was accumulated on the surface of earth, which not only encroaches land but also pollutes the environment. In this study, low-grade bauxite with alumina content of 53.18 wt.% originating from Shanxi Yangquan and coal gangue with alumina content of 38.07 wt.% originating from Shanxi Datong were used to synthesize mullite materials. Bauxite and gangue were mixed by the ratio of 1 to 1. The ingredients were prepared according to the alumina content of 45.63 wt.% and 70 wt.%, by adding a certain amount of industrial alumina, respectively. The samples were sintered at 1350°C to 1600°C after being milled, dried and formed. The influence of alumina content and sintering temperature on the phase, microscopic morphology and properties of samples were discussed. The results show that, the main phases of the sample with the alumina content of 70 wt.% were mullite (more than 60 %) and corundum after being sintered for 4h at 1600 °C. The phenomenon of columnar mullite and granular corundum staggering had been observed. The bulk density and the bending strength of sample is 3.21 g/cm3and of 220.73 MPa respectively.

Preparation and Mechanism of Cordierite by Using Calcined Bauxite as Raw Material at Relatively Low Temperature

The cordierite was synthesized at relatively low temperature by pressureless sintering method, using calcined bauxite, talcum , quartz and feldspar as raw materials in this paper. The water absorption (Wa), porosity (Pa), bulk density (Db) and bending strength of samples have been tested, and the synthetic process and mechanism have been investigated by XRD, SEM, and so on. The results showed that the cordierite could be synthesized at 1280°C and the range of synthetic temperature is 1160~1300°C, when the sample was sintered at 1280°C for 2h, its bulk density and bending strength were 2.20g/cm3and 72.13MPa, respectively. XRD analysis showed that the main phase of sample was cordierite, the cordierite content was about 88wt%, and the minor phases were MgAl2O4spinel and corundum. SEM results showed that the samples were dense and the pore sizes were 5 μm~100μm, the grains were growth and development well, the grains size were 0.5μm~6μm. High reaction activity corundum and mullite were provided by calcined bauxite, then coupled with the role of feldspar, thus reduced the synthetic temperature of cordierite.

Utilization of water reed in production of various insulation panels

Abstract Some panels and particleboards were made from reed mats and blends of reed-wood chips to be used inside buildings for sound and heat insulations. It was seen that the outer layers of the reed body (spike) was almost water resistant and exceptionally resistant to the penetration of common adhesives. Therefore, the panels from stitched reed mats exhibited very poor mechanical strength. The sound transmissions of such panels (1–3 km/s) made with various combinations, however, were recorded to be excellent compared with that of particleboards made of wood (17 km/s). Blends of reed chips (2 cm) and wood chips, however, gave particleboards with better mechanical properties (5–17 MPa) than that of panels made from reed mats (2 MPa). An increasing amount of reed chips in tested particleboards was recorded to be improving both sound and heat insulations from 17 to 6 km/s and from 0.34 to 0.27 W/mK, respectively. The bending strength of samples, however, was reduced from 26 to 5 MPa. Thickness swelling was also noted to increase from 18% to 85% due to reed chips addition. It was concluded that the outer layers of water reeds should be modified via chemical and/or enzymatic methods to increase the interfacial bounds between adhesives.

Preparation of Calcium Hexaluminate Using Al<sub>2</sub>O<sub>3 </sub>and White Beach Sand from Western Australia <sub> </sub>

Calcium hexaluminate (CA6) because of its high stability, high melting point and low thermal conductivity properties make it as a new high-temperature insulation materials are valued. In this paper, chemical analysis and XRD were used to investigate the composition of the white beach sand mineral from Perth coast of Western Australia. The main composition of it was carbonate. White beach sand as calcium source respectively, and industrial alumina as aluminum source synthesized CA6 at 1550°C-1650°C for 3h. The results showed that: synthetic CA6 shapes in platelet crystalline. Influence of different amounts of alumina and sintering temperature on synthesis of calcium hexaluminate are studied.The main phase of the samples with different amounts of alumina which decrease or increase 5%, 10% and 15% alumina around theory are CA6. The porosity of the samples obtained is about 53%. The bending strength of Sample S-0 of theoretical ratio values up to 7.73Mpa. Sintering temperature from 1500°C to 1650°C is not conductive to the improvement of apparent porosity of CA6 materials.

Microstructure and mechanical properties of 8YSZ ceramics by liquid-phase sintering with CuO-TiO2 addition

The 8% (mass fraction) yttrium-partially-stabilized zirconia (8YSZ) ceramic was fabricated via liquid phase sintering at 1 200–1 400 °C by adding different mass ratios of CuO-16.7%TiO2 (molar fraction) as sintering aid. Relative density, microstructure, Vickers hardness and bending strength as a function of sintering temperature and additive content were investigated. The experiment results show that liquid phase sintering at low temperature can be realized through adding CuO-16.7% TiO2 to 8YSZ. The Vickers hardness and bending strength of samples with sintering aid are generally much higher than those of samples without sintering aid for all sintering temperatures, and increase with the increase of sintering temperature. When the addition content of CuO-16.7% TiO2 is beyond 0.5%, the relative density, Vickers hardness and bending strength decrease with the increase of the mass ratio of sintering aid. Low additions of sintering aid are beneficial to aiding densification; high additions of sintering aid are detrimental to the sintered properties mainly due to greater amounts of pores generated by the volatilization of oxygen with the eutectic reaction between copper oxide and titanium dioxide. It is found that the fine grain size and high relative density are two main reasons of the high bending strength and Vickers hardness of the materials.

Investigation on bonding quality of beech wood (Fagus orientalis L.) veneer during high temperature drying and aging

In the present study, the effects of high drying temperature and UV light induced aging on bonding quality of plywood manufactured from untreated and treated veneer layers were investigated. Rotary cut veneers with dimensions of 500 mm×500 mm×2 mm produced from beech (Fagus orientalis Lipsky) log were selected for topochemical, chemical and mechanical analyses. The veneer sheets were oven-dried at 100°C and 180°C after the peeling process. Afterwards, the surfaces were exposed to artificial UV irradiation in an UV chamber for 24 h, 48 h and 72 h representing natural sun irradiation of 2, 4 and 6 months, respectively. Topochemical distribution of lignin and phenolic extractives of the treated and untreated veneers was investigated on a cellular level using UV microspectrophotometry (UMSP). For the chemical characterization of accessory compounds high performance liquid chromatography (HPLC) was used. Furthermore, the shear and bending strengths of plywood manufactured from the treated samples are determined in order to study the bonding quality. The UV microscopic detection shows that after high drying temperature and aging treatment, lignin condensation occurs. With increasing drying temperature and aging duration, more phenolic extractives are situated in parenchyma cells and vessel lumens which can be proved by increased absorbance at 278 nm. The HPLC analysis of the treated tissue showed distinct signals of polymerized compounds such as catechin and 2,6-dimethoxybenzoquinone which are chromophoric compounds in discolored beech wood. The mechanical properties of plywood showed that with increasing drying temperature up to 180°C does not negatively affect shear and bending strengths of samples. After exposure of the veneers to UV irradiation (especially 6 months), decreasing shear and bending strengths of plywood samples can be observed.

Research on Correlation between Formula of Steel Slag Ceramic (CaO-MgO-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> System) and Macro Property

This paper demonstrated a new approach to the utilization of steel slag and provided a pattern for steel slag ceramic synthesis. Based on previous research on steel slag (converter slag) applied as raw material of ceramic and directed at content of steel slag CaO-MgO-Al2O3(5wt%)-SiO2 system phase diagram was utilized in steel slag ceramic formula designing and augite region was selected. Bending strength of sample could reach 62.26MPa which was higher than national standard. When the content of steel slag was 40wt%, the steel slag ceramic would perform rather high bending strength. Through XRD patterns demonstrated the dominated crystal phases of all ceramic samples were pyroxene group crystals, akermanite existed in some samples also. But bending strengths of ceramics containing akermanite were lower than of samples containing pyroxene purely. Hence, diopside could be considered as the factor of improving ceramic bending strength.