Amorphous Phase Content Research Articles

Application of Rietveld refining method for the production of geopolymeric binders

The activated alkaline materials constitute a group of eco-efficient binders. For materials with a low calcium content, excess free sodium in the alkaline activation process results in efflorescences that weaken the matrix. The excess of free sodium occurs due to failures in the quantification of the reactive fraction consumed by the alkaline activation reactions. The present work compares the conventional dosage methods with the method used by the Rietveld refinement, based on the application of the external standard (EP). To determine the amorphous phase content in the materials, chemical (XRF) and mineralogical (XRD) analyzes were performed on metakaolin and silica fume. The formulations were then dosed using both methods, the molar ratios of Na2O/Al2O3 and SiO2/Al2O3 varying between 0.8 and 1.4. and 3.3–3.6, respectively. The activated alkaline matrix dosed by the EP method exhibited mechanical resistance approximately twice as high as that dosed by the conventional method. The formulation EP-3.6–1.0 showed greater mechanical strength, in addition to high resistance to dissolution in hydrochloric acid (52% of the material remained indissoluble). The optimal SiO2/Al2O3 and Na2O/Al2O3 molar ratios were equal to 3.6 and 1.0, respectively, approaching works that used precursors with a high degree of amorphism.

Microstructure of CEM II/B-S Pastes Modified with Set Accelerating Admixtures.

The presented paper aims to describe the influence of accelerating admixtures on the properties and microstructure of cement pastes and mortars. Blended slag cement CEM II/B-S containing two different clinkers (differing amounts of siliceous and aluminous phases) and four types of accelerators (calcium nitrate, sodium hydroxide, cement kiln dust, and crystal seeds) were used in research. Compressive strength tests (after 12, 24, 48 h of curing), Scanning Electron Microscope (SEM) observations together with an Energy Dispersive Spectroscopy (EDS) analysis, Mercury Intrusion Porosimetry (MIP) tests, and X-ray diffraction (XRD) analysis were conducted. Results have shown that SEM and EDS examination of the microstructure of cement pastes modified with accelerating admixtures at the observed points did not reveal differences that would be sufficient to explain the changes in compressive strength. Still, the increase in amorphous phase content indicates a faster hydration reaction rate for all pastes modified with accelerating admixture. It is backed up also by lower non-hydrated compounds content. All admixtures accelerate the hydration reaction of calcium silicate phases of cement, but only NaOH and cement kiln dust (CKD) influence the aluminate phase reaction rate. The pore volume is independent of the clinker type, while the pore size distribution is not.

Influence of chemical vapor precursor flow rate on the structure and thermal stability of phase-modulated VSiCN/Ag coatings

Ceramic/silver coatings are of interest for tribological and antimicrobial applications. Here, the amorphous phase volume fraction in VSiCN/Ag coatings was varied and the microstructure, mechanical properties, and vacuum annealing behavior of the phase-modulated VSiCN/Ag coatings were compared with columnar VN/Ag coatings. The coatings were deposited by filament-assisted reactive magnetron sputtering in a gas mixture of argon, nitrogen, and hexamethyldisilazane (HMDS). HMDS vapor flow rates were varied to influence coating amorphous phase content (0 at. % ≤ Si ≤ 10 at. %, 0 at. % ≤ C ≤ 20 at. %), and the sputter power supplied to a V58Ag42 target was manipulated to control metal content (3 at. % ≤ Ag ≤ 8 at. %). Silver surface segregation did not occur during coating growth, nor immediately after deposition. VN/Ag coatings exhibited columnar growth structures with >100 nm B1-VNx grains and 10−50 nm silver inclusions, which preferentially decorated the column boundaries. Columnar growth was completely disrupted in the VSiCN/Ag coatings and discrete silver inclusions were not observed within the microstructure. The hardness of all coatings was similar (12.3–16.5 GPa), while the apparent Young's modulus decreased from 247 to 169 GPa with increasing amorphous phase content. Rockwell indentation tests revealed that coating adhesion began to suffer after deposition at higher HMDS flow rates. Silver surface segregation was observed on all coatings after vacuum annealing at 550 °C for 1 h. The size of the surface particles ranged between 50 and 200 nm for the VN/Ag coating but was below 20 nm for the VSiCN/Ag coatings. Silver segregation occurred preferentially at coating growth defects in the columnar VN/Ag coating while the particle distribution was uniform across the surface of the VSiCN/Ag coatings. The results of this study demonstrate that phase modulation of ceramic/silver coatings may enable high-diffusivity microstructural features to be tailored for improved thermal stability and control of silver surface segregation at elevated temperatures.

Hydration-induced thermal behavior of crystalline and amorphous dispersed alumina

• The high-throughput express diagnostics realized using quantitative infrared thermography (QIRT) allows us to identify the amorphous phase in polymorphic alumina by the analysis of hydration-dehydration-induced thermal effects. • Unlike crystalline alumina, the amorphous one produces a pronounced excess heating in the hydration process. • In a humid atmosphere, the solid-state exothermic chemical reaction of the oxide transformation into crystalline hydroxide takes place • The pseudoboehmite phase formation during the rehydration process occurs exclusively due to the amorphous alumina interaction with water. Dispersed alumina is one of the main materials used in adsorption and catalytic technologies. However, some poorly controlled factors (exposure to the atmosphere, etc.) can change the oxide phase composition and morphology. Hence, it follows that the development of robust approaches to characterizing the material structure is a topical problem. In this study, the ability of high-performance quantitative infrared thermography (QIRT) to identify the amorphous phase in polymorphic alumina by the analysis of hydration-dehydration-induced thermal effects is demonstrated. The QIRT-obtained findings were verified by a comparison with the XRD patterns measured on the same samples. It is revealed that, in a humid atmosphere, the solid-state exothermic chemical reaction of the oxide transformation into crystalline hydroxide takes place, and, unlike crystalline alumina, the amorphous one produces a pronounced excess heating in this process. Moreover, it is found that the pseudoboehmite phase formation during the rehydration process occurs exclusively due to the amorphous alumina interaction with water. It is shown for the first time that the high-throughput express diagnostics realized using QIRT allows us to determine the amorphous phase content in dispersed alumina and, potentially, in other materials for which this problem is relevant.

A Review on the Wear, Corrosion and High-Temperature Resistant Properties of Wire Arc-Sprayed Fe-Based Coatings.

Among different thermal spraying methods, arc-spraying has been widely used due to its low operating costs and high deposition efficiency. The rapid progress of cored wire technology in arc-spraying has increased possibilities for the preparation of new Fe-based coating materials with enhanced properties by adding reinforcement particles and alloying elements to suit the different applications. Fe-based coatings have been extensively used because of their high strength, toughness, lower production costs, and availability of raw materials. This makes them suitable replacements for Ni-based coatings in ambient and high-temperature applications. This review discusses the research status and developments of the arc-sprayed Fe-based coatings. The study specifically reviews the wear behavior, corrosion analysis, and high-temperature resistant properties of arc-sprayed Fe-based coatings, aiming to develop an understanding of the protection mechanisms for Fe-based coatings. The performance of the Fe-based coatings depends on the integrity of the coating structure. Optimizing arc-spraying parameters minimizes defects (pores, grain boundaries, unmelted particles, oxides, and microcracks) that deteriorate the coating properties. High amorphous phase content, ceramic reinforcement particles and alloying elements enhance the corrosion, tribological, and high-temperature resistant properties of Fe-based coatings. In high-temperature applications, Fe-based coatings form oxide scales that protect the coating from further oxidation; thus, it is important to select the optimum composition for the alloying elements.

Dense VSiCN coatings deposited by filament-assisted reactive magnetron sputtering with varying amorphous phase precursor flow rates

Phase-modulated VSiCN coatings were deposited with hot filament assistance by magnetron sputtering of a vanadium target in a gas mixture of argon, nitrogen, and hexamethyldisilazane (HMDS). HMDS flow conditions and total working pressure were varied to influence coating amorphous phase content (0 at.% ≤ Si ≤ 9 at.%). Scanning electron microscopy revealed that deposition with HMDS vapor disrupted columnar growth and increased coating growth rate by as much as 27% relative to a VN 0.8 reference. Coating surface morphologies were characterized by atomic force microscopy . A transition from a nodular appearance ( R q = 8.9 nm) for the VN 0.8 coating to a pitted appearance ( R q = 2.7 nm) for the coating containing 9 at.% Si was observed. X-ray diffraction analysis and transmission electron microscopy indicated that the VSiCN coatings contained a nanocrystalline B1-VC x N y phase and an amorphous phase, whose phase fraction increased with HMDS flow. The crystallographic out-of-plane preferred orientation of the VN 0.8 coating was (220) while all VSiCN coatings were (111) textured. Coating hardness and apparent elastic modulus were measured by nanoindentation . The VSiCN coating with 3 at.% Si exhibited the highest hardness of 31.4 GPa, which was 8.8 GPa greater than the VN 0.8 coating. Coating apparent elastic modulus decreased with increasing HMDS flow from 288 GPa to 188 GPa. All coatings exhibited excellent adhesion to stainless steel substrates as evaluated by the Rockwell indentation test . The disruption of columnar growth and incorporation of Si in VSiCN coatings is a possible method of improving the high temperature wear resistance of VN-based coatings. • Deposition of dense, non-columnar VSiCN coatings is demonstrated. • Hexamethyldisilazane (HMDS) vapor is used as an amorphous phase precursor. • Granular and pitted surface topographies are obtained with R q < 3 nm. • Coating preferred orientation is (220) for the VN 0.8 reference and (111) for VSiCN. • Hardness decreases from 31 GPa to 19 GPa with increasing amorphous phase content.

Carbonation-induced properties of alkali-activated cement exposed to saturated and supercritical CO2

Carbonation of well cement under high-temperature and high-pressure conditions is a significant concern in geological sequestration projects. This study evaluates the carbonation-induced properties of low to high calcium-based one-part alkali-activated cements (AACs) as an alternative to Portland oil well cement under reservoir conditions. Fly ash/slag-based AACs exposed to saturated (SAT) and supercritical (SUP) CO2 for 28 days were characterised using compressive strength, XRD and SEM tests. The strength properties of AACs increased with increasing slag content from 40% (low calcium AACs) to 100% (high calcium AACs) by weight of the binder under both SAT and SUP conditions. Aragonite is the major polymorph of CaCO3 in all AACs, irrespective of the type of CO2 exposure, and the highest aragonite content was observed in 100% slag AAC. The amorphous phase content decreased while the crystalline CaCO3 increased in carbonated AACs with increasing slag content, resulting in a dense microstructure in high calcium AACs. Sealing of microcracks and pores was observed in high calcium AACs with the accelerated precipitation of CaCO3 by reducing total porosity. Low calcium AACs resulted in a more highly porous carbonated microstructure than high calcium AACs under SAT and SUP conditions.

Optimizing the microstructure of a new machinable bioactive glass-ceramic

ObjectivesThis study aimed to optimize the crystallization process and the microstructure of a new bioactive glass-ceramic (GC) previously developed by our research group to obtain machinable glass-ceramics. MethodsDifferential scanning calorimetry (DSC) analyses were conducted to explore the characteristic temperatures and construct a semi-quantitative nucleation curve. The GC specimens were characterized by X-ray diffraction (XRD) and Rietveld refinement. Their brittleness index (B) and machinability were characterized and compared with IPS e.max-CAD®. Their Young's modulus, fracture toughness, and hardness were assessed. ResultsWe found that the maximum crystal nucleation rate temperature of this GC is ~470 °C. Treatments were designed based on the 1st DSC peak onset (570 °C), 1st peak offset (650 °C), and 2nd peak offset (705 °C) crystallization temperatures of lithium metasilicate (LS, LiSi2O3) and lithium disilicate (LS2, Li2Si2O5). Rietveld refinement indicated an increase in LS2 and a reduction in LS and amorphous phase for increased temperatures and longer treatment times. Their B values indicate good machinability compared with that of the control group based on statistical analyses. As expected, lower levels of LS2 increase the machinability regardless of the rotation speed adopted, leading to a greater depth of cut and reduced Edge Chipping Damage Depth (ECDD). ConclusionThis bioactive GC with optimized microstructure presents high machinability. For treatment temperatures above 570 °C, the number of elongated LS2 crystals increases and decreases the amorphous phase content, which reduce the machinability of the GC, and should therefore be avoided. The best results were obtained using heat treatment at 570 °C, which produces LS crystals embedded in a glassy matrix (67%) with small contents of secondary phases.

Research on the influence of laser scanning speed on Fe-based amorphous coating organization and performance

The laser cladding method was selected to prepare Fe47Cr15Mo14Co3C15B6 amorphous coating on H13 steel surface. The structure morphology and surface properties of the cladding layer under various laser scanning speeds were compared, which were analyzed through scanning electron microscope, electron probe and X-ray diffraction to represent the micro microstructure and phase distribution of the cladding layer. The results show that, with the increase of scanning speed, there is obvious changes of the microstructure of the cladding layer. When the scanning speed was 50 mm/s, the cladding layer was made up of large amount of crystalline phase and small amount of amorphous phase. When the scanning speed was 80 mm/s, the proportion of amorphous phase in the cladding layer increased obviously, and the crystalline phase diffused in the amorphous region. When the scanning speed further increased, the amorphous phase content increased as well. In addition, with the increase of scanning speed, the hardness and corrosion resistance of the cladding layer increased greatly as well, which indicates that the amorphous phase amount has a significant influence on the properties of the cladding layer.

Preparation, characterization and rheological analysis of eco-friendly road geopolymer grouting materials based on volcanic ash and metakaolin

Geopolymer has been applied in road engineering as an environmentally friendly material. This study prepared geopolymer road grouting pastes in different mixture ratios of volcanic ash (VA) and metakaolin (MK). The mechanical properties, setting time, bleeding and expansion ratio, fluidity and expansion ratio, time-dependent rheological analysis were systematically evaluated. Finally, the microscopic experiments, including X-Ray Diffraction, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy with Energy Dispersive Spectrometer (SEM-EDS), were conducted to investigate the mechanism of geopolymerization based on VA and MK. The results showed that the mechanical strength increased with the content of MK. The flow curve of all pastes fitted the Bingham model. With the increase of MK content, the yield stress and plastic viscosity coefficient increased, which is because the stacked multilayer gullies microstructure aggravated the internal friction of paste particles, which led to decreased expansibility and pumpability. When the mass ratio of VA/MK was 1:0.33, the paste achieved the balance of mechanical strength and rheological properties with superior water retention and deformation resistance. The microscopic experiments showed that MK's mechanism enhanced the mechanical strength of geopolymer due to its high content of amorphous phases, smaller average particle size, and rich content of Al element. The SEM-EDS indicated that the MK improved the mechanical strength also by the improvement of nucleation effect. VA and MK complement each other in mechanical strength development under room temperature and fluidity, which are expected to be an alternative for cement as an eco-friendly road grouting material.

Structural and mechanical properties of Ti-B-C coatings prepared by dual magnetron sputtering

The films in Ti-B-C system have been deposited onto Si (100) substrates by dual direct current magnetron sputtering of Ti-B and graphite targets. During deposition, the sputtering parameters at the Ti-B target were unchanged, and the carbon content in films was controlled by variation of sputtering current at the graphite target in the range of 0-250 mA. The films were characterized in terms of their structure, composition, and mechanical properties. The X-ray diffraction measurements showed that all the films contain only one TiB2 crystalline phase of prominent (001) and (002) textures.The film hardness first increased with the increased carbon content due to the reduced grain size reaching maximum value of about 51.5 GPa for films deposited with 200 mA sputtering current, and then it is started to decrease due to the increased content of a softer amorphous phase. The friction coefficient steadily decreased with increasing film hardness. First-principles calculations together with the experimental results have made it possible to assume that the deposited Ti-B-C films consist of nanocrystals of solid solution TiB2-xCx surrounded by amorphous B-C-O phase.

Amorphous ZnO modified anatase TiO2 thin films templated by tripropylamine and their electrical properties

In the present study we report on a low cost synthesis of amorphous ZnO modified anatase TiO2 (40 and 20 mol% ZnO) thin films deposited via sol-gel spin coating technique on glass substrate. The effects of the composition on the structural, morphological and surface chemistry properties were discussed and correlated with the electrical behavior. Thus, by X-ray diffraction and Raman spectroscopy only TiO2 indexed in the anatase crystalline structure was identified without any ZnO characteristic crystalline phase. The surface chemistry assessed by X-ray Photoelectron spectroscopy highlighted the presence of Ti4+ in TiO2 as well as the presence of Zn2+ coordinated in the amorphous ZnO proved by the Auger ZnLMM transition shifted toward lower binding energies. The films are continuous, homogeneous with grain size below 20 nm and exhibit an intergranular porosity, as it was displayed by Scanning Electron Microscopy.The sensor signal towards CO exposure is strongly related to the amount of the ZnO amorphous phase formation. Thus, we found that a higher content of the ZnO amorphous phase leads to a lower sensitivity. The electrical and sensing measurements were performed in the temperature range (room temperature 400 °C), over the range of CO concentrations (0-2000 ppm). The sensor containing 20 mol.% amorphous ZnO exhibits a good sensitivity at ~300 °C for a low CO concentration .

Understanding of crystallization behaviors in laser 3D printing of bulk metallic glasses

In 3D printing of bulk metallic glasses (BMGs) by selective laser melting (SLM), partial crystallization normally occurs in heat-affected zones (HAZs), which significantly deteriorates the properties of 3D-printed BMGs. To understand which factor dominates amorphous-to-crystalline conversion of 3D-printed BMGs, two representative BMG alloys with different glass forming ability (GFA), i.e., Zr55Cu30Ni5Al10 (named as Zr55 with high GFA) and Zr60.14Cu22.31Fe4.85Al9.7Ag3 (named as ZrAg with low GFA), were selected for SLM 3D printing, and their crystallization behaviors were comparatively studied. It is revealed that the 3D-printed ZrAg BMG with low GFA always possessed a higher amorphous phase content than the Zr55 BMG with a high GFA under different laser energy inputs. Thermal analysis and TEM observations revealed that crystal growth rate is the crucial factor for the resistance against amorphous-to-crystalline conversion in 3D-printed BMGs, as the ZrAg system exhibited much lower crystal growth rate although it has a lower GFA. The different crystal growth behavior of the two BMGs is associated with their different crystallization mechanisms: ZrAg BMG follows the mode of primary-type crystallization with multiple phases formation, leading to a low crystal growth rate, while Zr55 BMG follows the mode of polymorphous-type crystallization, which is characterized with formation of a simple crystalline phase, thus leading to a high crystal growth rate. The present work sheds light on the understanding of crystallization mechanism in 3D-printed BMGs and provides a guide for selection or design of BMG compositions for 3D printing.

High Effective Preparation of Amorphous-Like Si Nanoparticles Using Spark Erosion Followed by Bead Milling.

This work aims to prepare the silicon nanoparticles with the nanocrystal-embedded amorphous structure through spark erosion followed by bead milling. Spark erosion breaks up monocrystal silicon ingots into micro/nanoparticles, refines the crystal grains, makes the crystals randomly disordered, and increases isotropic character. Bead milling further refines the crystal grains to a few nanometers and increases the amorphous portion in the structure, eventually forming an amorphous structure with the nanocrystals embedded. Spark erosion saves much time and energy for bead milling. The crystallite size and the amount of amorphous phase could be controlled through varying pulse durations of spark discharge and bead milling time. The final particles could contain the nanocrystals as small as 4 nm and the content of amorphous phase as high as 84% and could be considered as amorphous-like Si nanoparticles. This processing route for Si nanoparticles greatly reduced the production time and the energy consumption and, more importantly, is structure-controllable and scalable for mass production of the products with higher purity.

Effect of Carbonate on Desilication of Sodium Aluminate Solution at High Temperature

Carbonate is the main anionic impurity in alumina produced by the Bayer process. The phase composition, morphology, and precipitation activity of desilication products (DSPs) precipitated at 245°C in sodium aluminate solution with different carbonate concentrations have been investigated by x-ray diffraction (XRD) and scanning electron microscopy–energy-dispersive x-ray spectroscopy (SEM–EDS) methods. The crystalline DSPs without carbonate are composed of zeolite, sodalite, and hydroxy-sodalite, but only zeolite and cancrinite precipitate in the presence of carbonate. Increasing the carbonate concentration promotes the precipitation of cancrinite but reduces the crystallinity of various DSPs. The cell parameters and the Na2O/Al2O3 ratios of DSPs are significantly increased because of the entry of sodium carbonate during crystallization, especially for the cancrinite. The morphology of various DSPs is greatly changed by the carbonate. The amorphous phase content and precipitation activity of DSPs increase with increasing carbonate concentration. This contributes to the effective removal of carbonate from sodium aluminate solution by controlling the desilication process.

Stripping voltammetry of nanoscale films of Zn–Ni alloy

Nanoscale Zn–Ni alloy films of ~ 20…90 nm thickness were obtained from ammonia-glycinate electrolyte in the potential range from − 1.15 to − 1.475 V. Chemical and phase composition of films were analyzed by stripping voltammetry in alkaline ammonia-glycinate electrolyte. It is shown that the method of stripping-voltammetry in this electrolyte allows estimation of the content of both crystalline and amorphous phases of Zn–Ni alloy, including films with small content of components. All alloy films contain a γ-phase in the mentioned range of potentials. Its maximum content (95%) is observed at a potential of − 1.2 V corresponding to the beginning of the limiting current on the polarization curve of the alloy deposition. Despite the fact that Zn is a more negative metal in the zinc–nickel pair, its content in the alloy decreases with an increase in the polarization of deposition due to anomalous codeposition of Zn with Ni. As the Ni content increases, the contributions of the β-phase and the Ni-phase increase. It is shown that in an electrolyte of the same composition, layers of an alloy of different chemical and phase composition are deposited depending on the potential. Results can be useful both for analyzing the composition of films obtained from other electrolytes, and for choosing the architecture of multilayer coatings deposited by the single-bath method.

Biocomposites based on the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) matrix with the hemp fibers: thermal and mechanical properties

The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was used to prepare biocompatible composites modified by the hemp fibers. The aim of the study was to assess the structure and selected thermal and mechanical properties of the obtained biocomposites. The morphology of samples was analyzed using a scanning electron microscope and a computed tomography analysis. The phase transitions of composites and polymer matrix were investigated using differential scanning calorimetry. Moreover, the non-equilibrium and equilibrium thermal parameters of composites and the unfilled PHBV were established based on the thermal history. Knowing equilibrium parameters, i.e., the heat of fusion for the fully crystalline materials, ΔHf (100%), and the change of heat capacity at glass transition temperature (Tg) for the fully amorphous, ΔCp (100%), composites, the degree of crystallinity, mobile, and rigid amorphous fractions were estimated. The addition of hemp fibers to the PHBV matrix caused around a two-time increase in the degree of crystallinity in reference to the unfilled PHBV. It was also observed that the addition of hemp fibers caused a decrease in heat capacity for fully amorphous material for all the biocomposites obtained. A similar relationship was observed in case of values of the heat of fusion for fully crystalline material. Simultaneously, the decrease in amorphous phase contents was noted. It was also noted that the rigid amorphous fraction exists only for the unfilled polymer matrix. Some mechanical properties of investigated materials were also measured and presented.

Influence of mechanical alloying on the particle size, microstructure and soft magnetic properties of coarse Fe-based amorphous powders prepared by gas atomization

The aim of this work is to refine the particle size of the coarse Fe-based amorphous powders by ball milling process without destroying the amorphous characteristics, thermal stability and soft magnetic properties. The gas atomized Fe-based amorphous powders were sieved, and the powders larger than 75 μm were selected as the raw materials. The effects of ball milling on the particle size, morphology, amorphous rate, thermal stability and soft magnetic properties of the Fe-based amorphous powders were systematically investigated. The results showed that the particle size of the Fe-based amorphous powders decreased as the ball milling time increased, and the mass median diameter (D50) of the powders was reduced by almost 80% after ball milling of 9 h compared with that of the initial powders (D50 reduced from 138.4 μm to 24.22 μm). The nanocrystallization and amorphization induced by the microstructural breakdown and intensified inter-diffusion of elements during the ball milling improved the amorphous rate of Fe-based powders. The ball milling reduced the saturation magnetization of the Fe-based amorphous powders, and had little effect on the coercivity. As a result, ball milling not only refined the particle size, but also improved the amorphous phase content of the Fe-based amorphous powders without changing the thermal stability and soft magnetic properties.

Effects of Milling Variables in Amorphous Phase Formation of Fe&lt;sub&gt;78&lt;/sub&gt;Si&lt;sub&gt;9&lt;/sub&gt;B&lt;sub&gt;13&lt;/sub&gt; Alloy Produced by Mechanical Alloying

In this study, amorphous Fe78Si9B13 alloy was successfully synthesized by mechanical alloying (MA) of pure elemental powders which were milled under an argon gas atmosphere. Effects of milling time on the phase transformation, microstructure and morphological evolution were studied by X-ray diffraction (XRD), laser diffraction (Granulometry), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that by increasing the milling time, the nanocrystalline and amorphous phase content increases and alloys with good properties are obtained at 100 h of milling.

Effects of sewage sludge ash produced at different calcining temperatures on pore structure and durability of cement mortars

The effects of calcining temperatures (ranging from 500 to 900 ℃) on the characterization of sewage sludge ash (SSA) and the pore structure and durability properties, including drying shrinkage and freezing–thawing resistance of SSA blended cement mortars are reported in this paper. The findings of this study indicated that the SSA displayed lower particle size and higher specific surface area in comparison to cement particles. The increase in the calcining temperature resulted in the lower loss on ignition and higher content of amorphous phase. The SSA calcined at 700 ℃ exhibited the highest pozzolanic activity index. Studies on the properties of SSA blended mortars showed that SSA had the effect of refining the pore size of matrix by means of micro-aggregate filling effect. The incorporation of SSA increased the drying shrinkage of mortars significantly. However, the refining effect of SSA on the pore structure can offset the frozen-heave stress and reduce the viscous resistance in the matrix, resulting in the enhancement of freezing–thawing resistance of mortars. The mortar containing SSA produced at 700℃ exhibited the lowest drying shrinkage and the highest freezing–thawing resistance.