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An in-depth understanding of the development of α phase have been proposed in a β-quenched Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe alloy during continuously heating process. Acicular α, striated α and string-like α were displayed at different temperatures. The acicular α formed at 390 °C gathered together in parallel to form clusters, which originated from the assisted nucleation of ω clusters. The striated α formed at 570 °C showed highly strained lattice inside with unique satellite reflections, referring to the displacive-diffusion formation mechanism of α phase. The string-like α formed at 690 °C was the result of the impingement of individual α phase. These results provided new insights into the phase transformation mechanism in the near β titanium alloys.

The underwater laser cladding layers of Ti-6Al-4V titanium alloy were prepared using underwater wire-feeding laser cladding (UWLC) technology under different heat inputs and gas flow rates. At optimum process parameters, the uniform underwater cladding layer without oxidation was obtained, and the cracks inside layer were restrained successfully. The deposition morphology, grain characteristics, microstructure and properties of the cladding layer were analyzed, and the mechanism of crack elimination was investigated. With the increase of heat input, the grain size and thickness of the α lath increased, while the amount of α' decreased, and the oxidation phenomenon had also improved. The sizes of columnar β-crystal grains and spherical β-crystal grains both increased. The microstructure of the different heat input layers was composed of lamellar α phase and acicular α′ phase with different sizes. Besides, the reduction of the cooling rate inhibited the unidirectional growth of acicular martensite, so that the martensite arrangement was close to a disordered state, and the deformation of the cladding layer was more uniform, which effectively prevented the cracks and melt expansion. The corrosion resistance of the coating was improved, and the microhardness was reduced.

Cordierite-acicular mullite composites containing 0, 25, 50, 75 and 100 wt% of mullite were fabricated from waste MoSi2 and commercial powders of Al2O3 and spinel (MgAl2O4). Careful oxidation of pulverised waste MoSi2 rendered a precursor mixture of MoO3 and amorphous SiO2, which served as pore forming agent and SiO2 source, respectively. Evaporation of MoO3 at ∼750 °C allowed production of highly porous cordierite-mullite ceramic composite after sintering in air at 1350 °C for 4 h. The combination of equiaxed cordierite grains and elongated (prism-like) mullite grains, resulted in unique microstructure with open porosity between 53.3 and 55.6 vol% which makes the obtained composite convenient for application as diesel particulate filter material. The presence of mullite affected four key thermo-mechanical properties which determine the thermal shock resistance of cordierite-mullite composite. The best thermal shock resistance was measured in composite containing 75 wt% of mullite. It was a result of improved thermal conductivity (1.081 W/mK) and bending strength (3.62 MPa) and relatively low values of coefficient of thermal expansion (3.8 × 10−6 K−1) and elastic modulus (2.27 GPa).

Synergistic composite catalysts have always been the research focus of water splitting. Whereas, amorphous phases usually occurred on grain boundaries, which greatly hinders electron transfer and reduces the catalytic performance. Herein, a NiWSe@NF acicular nanowire electrode was fabricated by a simple hydrothermal strategy, affording outstanding activity and durability, requiring overpotentials of only 103 mV (HER) and 203 mV (OER) under 10 mA cm−2, respectively. Experimental studies and theoretical analysis demonstrate that the excellent catalytic activity is attributed to the interpenetrate structure, which eliminates the formation of amorphous phase and provides a high-speed channel for electron transmission. The crystal interpenetration on grain boundaries adjusts the electronic, promotes the intermediates adsorption and reduce reaction energy barrier. The super-hydrophilic arisen from crystal interpenetration would also reduce the adhesion of generated bubbles and avoid performance attenuation. This work provides a new perspective for the development of high-efficiency composite catalysts.

Background Effective high-throughput strategies to prepare nanostructured electrodes for glucose sensing remain significant interest for many applications. In this study, acicular nickel was immobilized on carbon nanofibers (CNFs) via electroless plating under a magnetic field to form CNFs-Ni, and its application as an electrode in amperometric non-enzymatic glucose sensing was investigated. Methods Polyacrylonitrile (PAN) nanofibers (NFs) were fabricated by centrifuged-electrospinning, in which the combination of electrostatic and centrifugal forces produces a strong stretching force. PAN polymer chains were aligned parallel to the axis of the NFs, thereby stretching the dispersed PAN droplets into thin and molecularly orientated NFs. The PAN NFs were then subjected to stabilization followed by carbonization at 1200, 1300, 1400, or 1500 °C to produce PAN CNFs. The characteristics of the CNFs were confirmed by scanning electron microscopy (SEM), electron spectroscopy for chemical analysis, Raman spectroscopy, and four-point probe analysis. Additionally, the CNFs coated with acicular nickel (CNFs-Ni) were analyzed by SEM, X-ray diffraction, and high-resolution transmission electron microscopy. Significant Findings Under the optimal conditions (CNFs1400-Ni), the glucose sensor showed a high sensitivity (7404 μA mM−1 cm−2) with a linear range from 2.1 × 10−2 to 6.0 × 10−1 mM (R2 = 0.993) and fast response (10 s).

Carbon diffusion at the solid–liquid interface is of fundamental importance in scrap melting. Herein, the scrap microstructure at the melt interface and the carbon and silicon distributions are described using optical microscopy and electron microprobe analysis (EPMA). The microstructural path from the surface to the interior of the scrap was primary carbide → acicular martensite → dislocation martensite (original structure). The corresponding carbon concentration gradient was > 4 wt.% → 1–1.5 wt.% → 0.2 wt.%. This was consistent with the observed microstructural changes. Furthermore, the depth of the carbon diffusion layer was 200 μm and 220 μm at 1300°C and 1350°C, respectively. The silicon-enriched layer may be a retarding factor for carbon dissolution. The area of the austenite phase region in the Fe-Fe3C phase diagram was reduced owing to the presence of silicon. Therefore, acicular martensite formed after water quenching decreased, which reduced the thickness of the carburized layer.

The traditional welding processes are challenging to obtain an excellent jointed structure with a thickness of over 80 mm. Meanwhile, cyclic heating for large-scale manufacturing components worsens microstructure and mechanical properties after welding. Laser Melting Deposition (LMD) technology is put forward to break through the limit of large-scale jointing components widely used for manufacturing aerospace products. Therefore, the LMD experiment with coaxial powder feeding for joining a pair of X-groove Ti-6Al-4V thick plates (80 mm) with different thermal behaviors (including laser scanning speeds and cooling rates) is carried out in this paper. The morphology evolution of its microstructure at the equiaxed grain zone (EQZ) and the deposition area under different thermal behaviors are systematically investigated. Meanwhile, the relationship between microstructure evolution mechanism and tensile properties is further explored. The volume fraction and size of acicular α/α' phases at the EQZ or the deposition area keep a stable rising when the laser scanning speed increase from 10mm/s to 20mm/s. The α-Ti cluster phases are usually precipitate around the β grain boundary with a low scanning speed and cooling rate. By contrast, the orthogonal acicular martensitic α/α' phase can precipitate inside the β grain, forming a Basketweave structure with a high scanning speed and cooling rate. The Basketweave structure forming in β grains can coordinate the deformation and reduce the stacking effect of dislocations, which is beneficial for improving ductility. However, the α-Ti cluster phases precipitating around the β grain boundary usually cause local stress concentration at these locations, forming microcracks at this location and deteriorating the tensile properties.

The microstructural evolution law and the α variant selection relationship, as well as the deformation mechanism of the HIPed Ti-6Al-4V alloy, were investigated under the conditions of thermal compression and subsequent heat treatment. The results showed that lamellar α phase bending/kinking and fragmentation were the main spheroidizing mechanisms in the α+β phase region (850°C and 920°C), DDRX occurred as the restoration mechanism in the near-β region (940°C), and the heterogeneous microstructure originated from the temperature gradient distribution. The strain rate clearly affected the dynamically recrystallized grain fraction and diameter, e.g... both the fraction and diameter increased at a lower strain rate. The acicular α precipitated from β phase at 940°C obeyed the Burgers relationship with β, and their misorientation angle intensified at approximately 60°. GBα formed by reducing the adjacent lamellar α misorientation angle; therefore, the GBα nucleation energy was lowest. The microhardness variation was relatively stable along the X direction at α+β phase region deformation, while oscillation appeared at near-β deformation, which can be explained by microstructure heterogeneity after thermal compression. For heat treatment, the trimodal microstructure appeared at 940°C/0.001 s-1/60% thermal compression and subsequent 950°C/1 h/WQ heat treatment, and the result might guide practical production to optimize mechanical properties.

Compared with the gas metal arc welding (GMAW), the cold metal transfer technology can significantly reduce the welding heat input owing to obtain the output current of almost zero in the droplet detaching, which has a greater advantage in additive manufacturing. In this work, the cold metal transfer was employed to study the law of appearance and mechanical behavior of additively manufacturing of Ti–6Al–4V alloy. The results showed that the continuous and uniform weld appearance could be obtained when the current of 120 A–130 A was used. In the top layer, middle layer and bottom layer of thin-walled components, the same microstructure was obtained with the different parameters, which were mainly consisted of the columnar original β grains and acicular martensite α’. The max-hardness was obtained in the bottom zone (BZ) of thin-walled component. With the increase of welding current, the hardness values in BZ were decreased. With the increases of current, the tensile strength was reduced, which caused by the grain growth.

In current research, aluminium oxide and silicon dioxide are used as raw materials for fabricating main structures of mullite diesel particulate filters. The variable substances applied to develop acicular mullite structure are titanium dioxide, aluminium fluoride, and vanadium oxide. Carbon black was used to create pores in mullite diesel particulate filters with 35 to 45% porosity based on the sintering temperature of 1300°C. The images of the filter’s porous surface microstructure were investigated using scanning electron microscopy. Vanadium oxide and aluminium fluoride play important roles in growth of acicular shape and acicular size for membrane, respectively. Acicular size of membrane varies from a hundred nano-meters to the submicron in needle diameter. The relation of all factors between pore size, porosity, surface roughness, and pin-shape microstructure can be controlled by additional amounts of additives. From Raman spectroscopy analysis, the soot formation of carbon black’s micro and nanostructure are acceptable to simulate diesel soot particles. In line with these results, carbon black was successfully used as a substitute of real engine soot in soot kinetics reactivity. In addition, the oxidation kinetics of soot particles on mullite and acicular mullite membrane were investigated by using tight contact in isothermal and loose contact in non-isothermal thermo-gravimetric analysis. The calculated apparent activation energies of soot oxidation with isothermal technique on mullite and acicular mullite membrane are approximately 213 and 141 kJ/mol while those values calculated with non-isothermal technique are 118 and 76 kJ/mol, respectively.

In order to reveal the precipitation behavior and strengthening mechanism of extruded 2196 Al-Cu-Li alloy plate during aging treatment, one-step and two-step age-hardening treatment with different temperatures and time were conducted. According to the mechanical property tests and microstructure observation, it was found that the strengthening effect of two-step age-hardening treatment is better than that of one-step aging, and the plasticity of the alloy is also improved. This is because the Guinier–Preston zones precipitated during low-temperature pre-aging can provide nucleation particles for T1 phases in the second-stage aging process, thus promoting the uniform precipitation of fine acicular T1 phases. In addition, the size of θ' phase and grain boundary precipitates in the two-step aged alloy is small, and the width of precipitated free zone is also narrow, which promotes the improvement of mechanical properties of the plate. The optimal two-step age-hardening treatment of 2196 alloy is finally determined as 125 °C×8 h+165 °C×32 h, the yield stress reached 455 MPa, and the fracture mechanism of the corresponding alloy shows a combination of intergranular fracture and cleavage fracture.

This paper aims at analyzing the effect of heat treatment using Concentrated Solar Energy (CSE) on the martensitic microstructure evolution of Ti-6Al-4V alloy manufactured by Selective Laser Melting (SLM) technology. The application of CSE, a renewable energy sources, in post-processing of SLMed Ti-6Al-4V alloy is discussed based on heat treatments performed at Plataforma Solar de Almeria, Spain, using solar furnace SF40. In SLM process of Ti-6Al-4V powder because of local high heating followed by a rapid cooling the microstructure consists of an acicular martensite (α′ phase). Decomposition of α′ martensite of SLMed Ti-6Al-4V after heat treatment in solar furnace, using CSE, by SEM, EDX, TEM, SAED, and XRD analyses, was investigated. It has been found that for treatment below β-transus at 705 °C, because of low temperature, the α′ martensite was not fully converted into α + β and the β phase was not identified by XRD analysis. Heat treatments below (940 °C followed by 650 °C) and above (1050 °C) β-transus have revealed that α′ martensite was converted into a lamellar α + β mixture and also β phase was identified by XRD and TEM analysis. In the analyzed areas, middle areas of the samples contain an area fraction of β phase greater than the top areas. Area fraction of β phase, after heat treatment above β-transus, at 1050 °C, is greater than that obtained after treatment below β-transus.

The microstructure of additively manufactured Ti-6Al-4V (Ti64) produced by a laser powder bed fusion process was studied during post-build heat treatments between 1043 K (770 °C) and just above the β transus temperature 1241 K (1008 °C) in situ using high-energy X-ray diffraction. Parallel studies on traditionally manufactured wrought and annealed Ti64 were completed as a baseline comparison. The initial and final grain structures were characterized using electron backscatter diffraction. Likewise, the initial texture, dislocation density, and final texture were determined with X-ray diffraction. The evolution of the microstructure, including the phase evolution, internal stress, qualitative dislocation density, and vanadium distribution between the constituent phases were monitored with in situ X-ray diffraction. The as-built powder bed fusion material was single-phase hexagonal close packed (to the measurement resolution) with a fine acicular grain structure and exhibited a high dislocation density and intergranular residual stress. Recovery of the high dislocation density and annealing of the internal stress were observed to initiate concurrently at a relatively low temperature of 770 K (497 °C). Transformation to the β phase initiated at roughly 913 K (640 °C), after recovery had occurred. These results are meant to be used to design post-build heat treatments resulting in specified microstructures and properties.

TiN/Ni alloying of 38CrMoAl steel surface was carried out by continuous scanning electron beam. The effect of electron beam process parameters on the surface microstructures and mechanical properties of 38CrMoAl steel was studied. The results shows that the sample surface was divided into three regions: alloying layer, heat affected zone and substrate. Alloying layer made up with equiaxed crystals and short columnar crystals, microstructure of the heat affected zone was acicular and lath martensite, microstructure of substrate was tempered sorbate. The microhardness of the sample section first increased and then decreased, at a depth of 400 μm, the microhardness reached a maximum of 817.9 HV. When the beam current reached 12 mA and the moving speed reached 5.5 mm/s, the surface microhardness of the sample reached the highest 1209HV and the abrasion loss reached the lowest 4.6 mg.

In this paper, a modification method of polypropylene (PP) films is proposed for capacitors by micro doping of carboxylated cellulose nanocrystals (C-CNCs). Results prove that crystallization process of films is promoted, due to the entanglement effect of acicular ultra-structures of C-CNCs on PP molecular chains. With a proper doping content (0.01 wt%), the thermal properties are elevated, and the DC conductivity decreases by raising crystallinity and limiting carrier movement. Modified films possess a restricted dielectric loss at low frequencies because of regular microstructures and decreased conduction loss. Based on DC experiments at different temperatures, the breakdown strength of C-CNC/PP films shows an increase by approximately 51% at 85 °C, basically equaled to the level of pure PP at 25 °C. The mechanism is attributed to deep trap sites, which are introduced by the large crystal region and result in short free path in carrier transport. This novel PP film shows a great potential for application under thermal-electrical compound field in power systems.

The deformation mechanism of the fine structure composed of primary α phase (αp) and acicular secondary α phase (αs) on quasi-static mechanical properties is still not very clear. The main controversy is focused on the role of αp in the mechanical behavior. In this paper, the microstructure of the heat-treated near β-type Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn alloy after tensile tests was observed by transmission electron microscopy (TEM). And the results showed that in the slight deformation region the dislocations were accumulated at the intersection of αp and β matrix separated by αs, while only a few dislocations nucleated in β matrix. In the severe deformation region, a large quantity of dislocations in both αp and β matrix were observed. It can be inferred that αp deformed firstly and then activated the deformation of β matrix, that is, the thickness of αp and the inter-particle spacing of αs played a dominant role in the deformation process. The quantitative relationship between the yield strength and the microstructure parameters is consistent with this inference. By adjusting the solution treatment parameters and the subsequent aging treatment, three fine structures were obtained, and the corresponding mechanical properties were determined. Furthermore, the yield strength can be described by the mathematical model σy ​= ​756.4 ​+ ​135.6/hp1/2 +32.2/ds1/2, where hp and ds are the thickness of αp and the inter-particle spacing of αs, respectively.

The influence of the evolution rule of basicity (0.6∼2.4) on the mineral composition and microstructure of sinter is studied by using a polarizing microscope, and the comprehensive application analysis of the drum index, vertical sintering speed, and yield of sinter shows that, over the course of an increase in basicity (0.6∼1.0), the mineral structure changed from the original porphyritic-granular structure to a porphyritic structure. At the same time, there was no calcium ferrite phase in the bonding phase at a basicity of less than 1.0; therefore, the downward trend of the three indicators is obvious. When the basicity was further increased to approximately 1.6, the main structure of the mineral phase changed from a corrosion structure to an interweaving corrosion structure. Because of the existence of a porphyritic-granular structure, the structure of the mineral phase was extremely inhomogeneous and most complex near the basicity of 1.6; although a small amount of calcium ferrite displayed an acicular structure, the drum index appeared to show a very low value. With an increase in basicity to 2.0, the mineral phase structure was dominated by an interweaving corrosion structure with a uniform framework, and the content of calcium ferrite reached the highest value. Moreover, a clear acicular structure developed, and the drum index also increased to the highest value. At a basicity of more than 2.0, a mineral structure began to appear and the corrosion, porphyritic-granular structure, and the drum index also showed a slightly declining trend. Therefore, in the actual production process, basicity should be avoided as far as possible at around 1.0 and 1.6 and it should be controlled at around 2.0. At the same time, based on the mineral facies data set of this paper, the convolutional neural network is used to carry out a simple prediction model experiment on the basicity corresponding to the mineral facies photos, and the effect is quite good, which provides a new idea and method for the follow-up study of mineral facies.

Complex investigations of anorthite-containing building ceramics based on clay and metallurgical sludge waste were conducted. Component compositions were selected to obtain ceramic products with anorthite as the predominant phase. The physicomechanical characteristics, phase formation, and morphology of the prepared ceramic samples were investigated. It was determined that the structure of the anorthite phase in the composition of ceramic samples forms at metallurgical sludge waste content ranging from 10 to 50 wt.%. The strength metrics of the ceramic samples increase on account of the prismatic and acicular crystals of the anorthite phase which are uniformly distributed throughout the ceramic body.

Nanoneedle structures on dragonfly and cicada wing surfaces or black silicon nanoneedles demonstrate antibacterial phenomena, namely mechano-bactericidal action. These air-exposed, mechano-bactericidal surfaces serve to destroy adherent bacteria, but their bactericidal action in the water is no precedent to report. Calcium carbonate easily accumulates on solid surfaces during long-term exposure to hard water. We expect that aragonite nanoneedles, in particular, which grow on TiO2 during the photocatalytic treatment of calcium-rich groundwater, exhibit mechano-bactericidal action against bacteria in water. Here, we showed that acicular aragonite modified on TiO2 ceramics prepared from calcium bicarbonate in mineral water by photocatalysis exhibits mechanical bactericidal activity against E. coli in water. Unmodified, calcite-modified and aragonite-modified TiO2 ceramics were exposed to water containing E. coli (in a petri dish), and their bactericidal action over time was investigated under static and agitated conditions. The surfaces of the materials were observed by scanning electron microscopy, and the live/dead bacterial cells were observed by confocal laser scanning microscopy. As a result, the synergistic bactericidal performance achieved by mechano-bactericidal action and photocatalysis was demonstrated. Aragonite itself has a high biological affinity for the human body different from the other whisker-sharpen nanomaterials, therefore, the mechano-bactericidal action of acicular aragonite in water is expected to inform the development of safe water purification systems for use in developing countries.

The effects of rare earth elements (La, Sm) on the high-temperature (250 °C) microstructure and mechanical properties of Al-Si-Cu alloys were analyzed. The experimental results show that with the addition of La and Sm, the α-Al was significantly refined, and the eutectic Si changed from acicular to rod-like and granular. XRD and SEM analysis shows that the rare earth phases in the alloy were mainly AlSiRe and AlRe. Fracture morphology observations show the fracture mode of the alloy changes from brittle and ductile fracture to ductile fracture. With the increase of La or Sm contents, the mechanical properties of the alloys at 250 °C increase at first, and then decrease. When the contents of La and Sm are 0.4wt.% and 0.2wt.%, the tensile strength of the alloy reaches maximum of 143.91 MPa and 201.48 MPa, respectively.

As is well known, titanium alloy precipitates when subjected to aging treatment, which poses great influence on its mechanical properties. Thus, solution and solution-aging treatments were conducted in this work, and the wear performance was investigated under different normal loads. The results showed that acicular α′ martensite in the original selective laser melted Ti–6Al–4V was decomposed into α + β phases after the solution treatment, and then Ti3Al nanoparticles clusters were further formed in the α-matrix after the solution-aging treatment. The coefficient of friction decreased straightly as the normal load was increased from 20 to 100 N, and the wear mechanisms were characterized by abrasion, adhesive and oxidative wears. The wear rate of solution and solution-aging treated samples increased significantly comparing to the as-built counterpart, but the increment of the solution-aging treated sample was smaller than that of the solution-only treated sample, because of the Ti3Al precipitation in the solution-aging treated sample. These particles provided ball-like effect, reduced material losses and stabilized the wear process. All these factors contributed to the improvement in wear properties of the parts made by selective laser melting.

Chirality is an indispensable integral of biological system. As an important part of organisms, chiral organic structure of bone has been extensively investigated. However, the chirality of bone minerals is unclear and not fully determined. Here, we report nine levels of fractal-like chirality of bone minerals by combining electron microscopic and spectrometric characterizations. The primary helically twisted acicular apatite crystals inside collagen fibrils and between fibrils merge laterally to form secondary helical subplatelets. The chiral arrangement of several subplatelets forms tertiary spiral mineral platelets. Further coherent stepwise stacking of mineral platelets with collagen fibrils leads to quaternary to ninth levels, which reconciled the previous conflicting models. The optical activities in the UV-visible, infrared and terahertz regions demonstrated chirality from atomic to macroscopic scales based on circularly selective absorption and Bragg resonance at different levels of chirality. Our findings provide new insight into the structural integrity of bone, osteology, forensic medicine and archaeology and inspire the design of novel biomaterials.

To investigate the age hardening behaviors in an α + β titanium alloy, Ti-5Al-2Fe-3Mo, microstructures after solution treatment at a temperature in the high α + β region, and subsequent aging at temperatures below or around 500 °C were analyzed by transmission electron microscopy (TEM) and atom probe tomography (APT). Age hardening depended on both aging temperature and time, and at a very early stage of aging, fluctuations of Ti and alloying elements occurred in the β phase with an interval of several nanometers. It is considered that spinodal decomposition occurred. Subsequently, an extremely fine acicular hexagonal-close-packed (hcp) phase having width similar to that interval was formed, which contributed to age hardening together with the internal stress fields created by spinodal decomposition. A model was proposed to explain the extremely rapid hardening phenomenon: O suppresses martensite transformation during cooling from the solution treatment temperature, and the extremely fine hcp phase is formed in a short time by shear transformation in the O-lean area created by spinodal decomposition. In the O-lean area, the martensite start (Ms) temperature increases as the O concentration decreases. The effect of β-phase stability on the microstructural evolution in the spinodal modulated structure was also discussed: Shear transformation and β zone formation may occur depending on the β-phase stability and O concentration distribution.

This study investigates the effects of melting sequence on the microstructure, substructure, and mechanical properties of SLM Ti6Al4V alloys. Acicular α′ martensite was observed in all the SLM samples, and the dimensions of the α′ phase were changed with the melting sequence. Twins appear between acicular α′ martensite, and a large number of dislocations were observed in the material and within α′ martensite. The density of twins and dislocations increased with increasing melting sequence from single melting to triple melting. Tensile strength properties including ultimate tensile strength and yield stress, and hardness increased with increasing melting sequence from single melting to triple melting. The present results clearly prove that the melting sequence plays a significant role in determining the microstructure, substructure, and mechanical properties of the SLM as-built materials.

Metal matrix composites (MMCs) have broad application prospects in high-end manufacturing fields. However, as typical MMCs, SiCp/Al composites have poor weldability due to the appearance of brittle phase, crack defects, and segregation phenomenon in the fusion welding process. Hence, this paper provides a magnetically assisted resistance spot welding (MA-RSW) method to achieve the reliable welding of SiCp/Al composites. The experimental results show that the MA-RSW technology can significantly extend the weld lobe by increasing the nugget diameter and decreasing the weld penetration, avoid the appearance of the acicular Al4C3, eliminate weld defects, and homogenize the distribution of the strengthening phase. This facilitates the transformation of the fracture mode from interfacial fracture (IF) to partial thickness fracture (PTF) at low welding current and to button pull (BP) at high welding current in lap-shear tests. Therefore, the weld strength, ductility, and energy absorption ability are greatly improved.

Nanoparticles with high roughness and complex surface have strong reflection and scattering ability for electromagnetic wave, which can extend the propagation path of electromagnetic wave in absorbing coating, thus exhibiting better microwave absorbing performance. Constructing complex surface has been considered as an effective way to improve the microwave loss ability of microwave absorbers. In this paper, a novel bowknot-like N-doped Co@C magnetic nanoparticle constituted by acicular structural units (BNCoC) has been designed and prepared. Its precursor (BNCoCP) is synthesized by solvothermal method and converted into BNCoC by subsequent vacuum calcination. The main structure of BNCoC is N-doped carbon with Co nanoparticles embedded in it. BNCoC contains dielectric and magnetic components that has both dielectric loss and magnetic loss capabilities. Under the synergistic effect of its unique structure, BNCoC exhibits excellent absorbing performance with a minimum reflection loss of −47.6 dB@11.0 GHz@2.7 mm. Furthermore, the effects of calcination temperature and filler content on microwave absorbing performance are investigated. The electromagnetic parameters are analyzed in depth to reveal the microwave loss mechanism. This work reports a novel high-efficiency microwave absorber with unique structure. It provides a new method for microstructure design of microwave absorbing materials.

This work deals with the effect of 0.67 wt% Gd addition on the microstructure and tensile properties of Mg–4Al–5RE (where RE represents La–Ce mischmetal) alloy produced by sand casting (SC), permanent mold casting (PMC), and high-pressure die casting (HPDC). The results show that Gd addition could refine the grains, but its efficiency decreases by increasing the cooling rate due to the shifting from SC to PMC and finally to the HPDC method. Meanwhile, the acicular Al11RE3 phase is modified into the short-rod or granular-like shape under the three casting conditions. Such refined and modified microstructures are due to the Al2(Gd, RE) phases, which act as the nucleation sites in both the α-Mg matrix and Al11RE3 phase. Also, the weakening grain refinement effect in the increased cooling rates can be attributed to the narrow constitutional undercooling zone. After Gd addition, the 0.2% proof strength of the SC and PMC alloys increases by about 16.9% and 12.7%, respectively, while in the HPDC alloy, it decreases by about 5.9%. The main factor in the strength increment of the SC and PMC alloys is the grain boundary strengthening due to grain refinement which is proved by modeling the related mechanisms, whereas weak secondary phases and grain boundary strengthening mechanisms in the HPDC alloy lead to strength reduction. After Gd addition, the elongation to failure of the SC, PMC, and HPDC alloys is significantly enhanced by about 34.8%, 20.2%, and 12.3%, respectively, due to the crack resistance nature of the modified short-rod/granular Al11(RE, Gd)3 phase compared to the acicular one.

In the present work, the laser-induction hybrid cladding technology with induction post-heating (post-LIHC) was utilized to deposit coatings on the full-scale rail surface, and the effects of different induction post-heating temperature on the morphology, microstructure and mechanical performance of the heat affected zone (HAZ) were first in-depth analyzed. Results indicate that with the increase of the average induction post-heating temperature (Ta) in post-LIHC, the microstructure of the HAZ first transforms from the fine acicular martensite structure to the composite structure of martensite and pearlite, then changes to the pure pearlite structure, and finally retransforms to the coarse martensite structure. Especially, the morphology of the “Martensite Zone” (MZ) in HAZ undergoes three remarkable change with Ta increasing: “flat-U-shaped” → “flat-W-shaped” → “vanished” → “flat-V-shaped”. Under the induction post-heating window of Ta = 508 °C ~ 565 °C, not only the MZ in HAZ can be inhibited absolutely, but also fine pearlite with much lower interlamellar spacing, smaller grain size and higher grain misorientation forms instead, making the strength and toughness are both enhanced significantly than the other three type HAZs and the rail substrate. In addition, increasing the induction post-heating temperature within the window of Ta = 508 °C ~ 565 °C can increase the interlamellar spacing and reduce the ferrite grain misorientation of the pearlite structure in HAZ, but has no obvious effect on the grain size therein.

The influence of different hot isostatic pressing regimes on microstructure, phase constitution, microhardness, tensile properties and deformability of TC4 alloy fabricated by selective laser melting (SLM) technology was studied. The results show that the microstructure of SLM TC4 alloy is composed of acicular martensite α’ phase, and the sample exhibits high microhardness and strength, but low plasticity. After hot isostatic pressing, acicular martensite α’ phase transforms into α+β phase, and with the increase of hot isostatic pressing temperature and duration, α phase with coarse lath is gradually refined, and the proportion of α phase is gradually reduced. Because of the change of phase constitution in SLM TC4 alloy after hot isostatic pressing, the grain refinement strengthening is weakened, the density of dislocation is reduced, so that both microhardness and tensile strength are decreased by around 20%, the elongation is increased by more than about 70%, even over 100%, compared with as-deposited TC4 alloy. When the hot isostatic pressing regime is 940 °C/3 h/150 MPa, the tensile strength and the elongation achieve optimal match, which are about 890 MPa and around 14.0% in both directions. The fracture mechanism of alloy after 940 °C/3 h/150 MPa HIP is dultile fracture. Hot isostatic pressing causes concave deformation of SLM TC4 alloy thin-walled frames, and the deformation degree increases with the increase of temperature.

This article analyzes the influence of high-speed melt quenching by extracting a suspended melt droplet of a Ta–Zr binary system. Two mixtures of powdered tantalum and zirconium are used with a tantalum content of 60 and 6%, respectively. The compositions after mixing were pressed under a pressure of 250 MPa in a steel mold on a hydraulic press. Sintering is carried out in a vacuum furnace at 1350°C and 10–3 Pa. High-speed quenching is carried out in vacuum under a pressure of 2 × 10–2 Pa by electron-beam heating and a rotating disk heat receiver. The thickness of the produced fibers is 15–80 μm. The experimental results of discrete fibers of Ta–Zr alloy and samples obtained by the fusing of the billet by electric beam hating (in an as-cast state) are analyzed and compared. It is established that the structure of rapidly quenched fibers of the alloy with 6 wt % Ta is comprised of grains of acicular shape with a size of 5–10 μm and the fibers with 60 wt % Ta have columnar dendrite structure. An analysis of the distribution of tantalum and zirconium across the transversal cross section of fiber demonstrates that, with a decrease in the cooling rate below 105 K/s in the alloy with a tantalum content of 60 wt %, monotectoid transformation occurs. It is revealed that the microhardness of rapidly quenched fiber of the alloy with 6 wt % Ta is 1.5 times higher than that of the same alloy without quenching, and for the alloy with 60 wt % Ta the same comparison demonstrates double dominance.

To assess if a WC-9.2wt%Monel 400 alloy properties could be improved using LENS, one alloy was deposited onto a heated substrate and a second alloy was subjected to laser remelting of the final deposited layer. Microstructural characterization was performed using XRD, FESEM, EPMA, and Raman spectroscopy. Multiple microstructures were observed with eutectic, fishbone, and Fe/W-rich dendrites present in the fusion zone at the substrate-alloy interface, while needle-like, triangular and blocky carbides were found in the central regions, with acicular microstructures in the surface region. The alloy deposited onto the heated substrate had less eutectic and more fishbone structures in the fusion region. The laser remelted surface layer had a more homogenous acicular structure with minimal binder pooling compared to the other alloys. The spheroidal, cast WC/W2C powder particles were found to have core-rim structures after laser sintering. These microstructural variations resulted in a gradient hardness profile from the substrate-alloy interface to the alloy surface. The surface hardness of the laser remelted alloy was found to be significantly higher compared to the other alloys.

Ti-6Al-4 V is a popular alloy in additive manufacturing (AM) due to its applications in the biomedical implants and aerospace industries where the complex part geometries allowed by AM provide cost and performance benefits. Ti-6Al-4 V goes through a β → α’ transformation after solidification which is known to experience variant selection, e.g., through the formation of clusters of variants which, when situated together, partially accommodate the strain of the phase transformation. During electron beam powder bed fusion AM, an in situ decomposition of α’ martensite occurs during the cyclic reheating caused by melting successive layers, resulting in α + β microstructures. How variant selection influences the evolution beyond the initial rapid cooling remains an open question. Using 3D electron backscatter diffraction, we provide a clearer understanding without ambiguity from sectioning effects of how α’ decomposes into microstructures with distinct morphologies and variant/intervariant distributions. We extract quantitative 3D information on the various intervariant boundaries networks formed in samples printed using three different electron beam scanning strategies. This shows that differing mechanisms during the decomposition result in a shift from self-accommodating clusters in an acicular microstructure, to either the preferred growth of six variants in a basketweave microstructure, or to a colony microstructure where variant selection is determined by prior-β grain boundaries. We propose a new representation of the misorientations arising from the Burgers orientation relationship, which we refer to as intervariant network diagram, to reveal how variant selection during the martensitic transformation and subsequent decomposition leads to the intervariant boundary networks observed. This holistic understanding of the microstructural evolution has the potential to allow tailoring of microstructures and properties for specific applications.

Cloudina is a globally distributed Ediacaran metazoan, with a tubular, funnel-in-funnel form built of thin laminae (ca. 1–10 μm). To what degree local environmental controlled morphology, and whether early diagenesis controlled the degree of calcification of Cloudina, is debated. Here we test these hypotheses by considering assemblages from four, coeval localities from the Upper Omkyk Member, Nama Group, Namibia, from inner ramp to mid-ramp reef across the Zaris Subbasin. We show that sinuosity of the Cloudina tube is variable between sites, as is the relative thickness of the tube wall, suggesting these features were environmentally controlled. Walls are thickest in high-energy reef settings, and thinnest in the low-energy, inner ramp. While local diagenesis controls preservation, all diagenetic expressions are consistent with the presence of weakly calcified, organic-rich laminae, and lamina thicknesses are broadly constant. Finally, internal ‘cements’ within Cloudina are found in all sites, and pre-date skeletal breakage, transport, as well as syn-sedimentary botryoidal cement precipitation. Best preservation shows these to be formed by fine, pseudomorphed aragonitic acicular crystals. Sr concentrations and Mg/Ca show no statistically significant differences between internal Cloudina cements and botryoidal cements, but we infer all internal cements to have precipitated when Cloudina was still in-situ and added considerable mechanical strength, but may have formed post-mortem or in abandoned parts of the skeleton.

The new mineral yurgensonite, ideally K2SnTiO2(AsO4)2, the first natural arsenate with species-defining tin, and the continuous isomorphous series between yurgensonite and katiarsite KTiO(AsO4) are described from sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. Yurgensonite and a Sn-bearing variety of katiarsite are associated closely with one another and with badalovite, pansnerite, yurmarinite, achyrophanite, arsenatrotitanite, hatertite, khrenovite, svabite, sanidine, hematite, cassiterite, rutile and aphthitalite-group sulfates. Yurgensonite occurs as sword-shaped crystals up to 0.01 mm × 0.05 mm × 1 mm or acicular to hair-like individuals up to 1 mm long, typically forming radial aggregates up to 2 mm across. It is transparent, colourless, white or pale beige, with vitreous lustre. The mineral is brittle, cleavage was not observed. Dcalc is 3.877 g cm-3. Yurgensonite is optically biaxial (–), α = 1.764(6), β = 1.780(6), γ = 1.792(6) and 2Vmeas. is large. Chemical composition (wt.%, electron-microprobe; holotype) is: Na2O 0.51, K2O 16.27, Rb2O 0.12, Al2O3 0.26, Fe2O3 4.33, SiO2 0.29, TiO2 10.17, SnO2 22.01, P2O5 0.14, V2O5 0.19, As2O5 40.20, Sb2O5 4.88, SO3 0.28, total 99.65. The empirical formula based on 10 O apfu is (K1.92Na0.09Rb0.01)Σ2.02(Sn0.81Ti0.71Fe3+0.30Sb5+0.17Al0.03)Σ2.02(As1.945Si0.03S0.02P0.01V0.01)Σ2.015O10. Yurgensonite is orthorhombic, Pna21, a = 13.2681(6), b = 6.6209(3), c = 10.8113(5) Å, V = 949.74(7) Å3 and Z = 4. The crystal structure was solved from single-crystal X-ray diffraction data, R = 5.02%. Yurgensonite belongs to the KTP-structure type. It is a Ti,Sn-ordered analogue of katiarsite. The structure contains chains of corner-linked alternating crystallographically non-equivalent octahedra M(1) and M(2). In yurgensonite, Sn4+ prevails in the M(2)O6 octahedron whereas the M(1) site is Ti4+-dominant. The new mineral is named in honour of the Russian mineralogist, geochemist and specialist in studies of ore deposits Professor Georgiy Aleksandrovich Yurgenson (born 1935).

This work aims to investigate the microstructure and mechanical properties of Ti6Al4V parts produced by selective laser melting (SLM) in the early stage of solid-state diffusion bonding process. A thermomechanical simulator is employed to carry out the experiment. In the experiment, three diffusion temperatures (850°C, 900°C, and 950°C) are adopted, and the pressure is kept constant. It is found that the higher diffusion temperature reduces the voids on the bonding interface and part interior, and thus it improves the mechanical properties of the joint. The diffusion bonding joints consist of criss-cross acicular α′ martensitic structure. The volume fraction of martensitic α′ decreases with the increase of bonding temperature. Finally, the underlying mechanism of morphological evolution on the diffusion plane is analyzed. The results provide insights on the bonding mechanism of SLM-produced Ti6Al4V in solid-state diffusion joining.

Effects of the weld microstructure and inclusions on brittle fracture initiation are investigated in a thermally aged ferritic high-nickel weld of a reactor pressure vessel head from a decommissioned nuclear power plant. As-welded and reheated regions mainly consist of acicular and polygonal ferrite, respectively. Fractographic examination of Charpy V-notch impact toughness specimens reveals large inclusions (0.5–2.5 µm) at the brittle fracture primary initiation sites. High impact energies were measured for the specimens in which brittle fracture was initiated from a small inclusion or an inclusion away from the V-notch. The density, geometry, and chemical composition of the primary initiation inclusions were investigated. A brittle fracture crack initiates as a microcrack either within the multiphase oxide inclusions or from the de-bonded interfaces between the uncracked inclusions and weld metal matrix. Primary fracture sites can be determined in all the specimens tested in the lower part of the transition curve at and below the 41-J reference impact toughness energy but not above the mentioned value because of the changes in the fracture mechanism and resulting changes in the fracture appearance.

X-ray diffraction (XRD) technique was adopted to test the mineral composition of quicklime-solidified loess with different lime-adding rates at different curing periods. Scanning electron microscopy (SEM) and nitrogen adsorption were used to analyze the microporous structure of the solidified loess. The unconfined compressive strength and limit moisture content of solidified loess were combined to analyze the evolution mechanism of mineral composition and microstructure of solidified loess with the change of curing period and clarify the mechanism of quicklime-solidified loess. The results showed reduced content of clay minerals and decrease in the number of large pores due to increase of hydrates and pozzolanic products during extended curing period. The solidified soil fabric transformed from a compact structure into a mesh structure composing of acicular crystal and cementation. The main reasons for strength increase and change of liquid and plastic limits with the lime-solidified loess after extended curing are the change of the substance and the microstructure.

In this research, cast magnesium alloys AZ31-xGd are assessed as anode material candidates for primary Mg-air batteries. The effects of Gd content in the microstructure, discharge behavior and electrochemical properties of cast AZ31 as an anode are studied through microstructure characterization, electrochemical measurements and battery discharge tests. Results indicate that the introduction of Gd can refine α-Mg grains. The discharge and electrochemical properties of magnesium alloys are improved by optimizing its composition. We confirm that the Al2Gd can restrain the kinetics of hydrogen evolution reaction. The acicular structure can connect the magnesium alloy matrix and reduce the chunk spalling. The data suggest that AZ31-5.8Gd alloy has the best self-corrosion resistance performance and discharge behavior among all prepared AZ31-xGd alloys. AZ31-5.8Gd can output a high specific capacity of 1411.8 mAh g−1 and a high energy density of 1153 mWh g−1 at the current density of 40 mA cm−2. The anode efficiency can reach up to 63.21%. The addition of Gd properly can optimize magnesium alloy microstructure and improve the discharge performance.

Heterogeneous microstructure-induced mechanical responses in EH420 shipbuilding steel welded joint by electro-gas welding processed have been systematically studied by scanning electron microscopy, electron backscatter diffraction and mechanical testing. Comparing with the coarse-grained heat-affected zone (CGHAZ), the weld metal presents higher toughness (129.3 J vs. 37.3 J) as it contains a large number of acicular ferrites with high-angle grain boundaries (frequency 79.2%) and special grain boundary ∑3 (frequency 55.3%). Moreover, coarse austenite grains in CGHAZ and slender martensite–austenite constituents between bainite laths may likely facilitate crack propagation. Polygonal ferrites and tempered pearlites formed at the junction of the fine-grained heat-affected zone and the intercritical heat-affected zone induced a softened zone with an average hardness of 185 HV0.5, which is the main reason for the occurrence of tensile fracture.

Iron ores always contain several forms of alumina, which may have different effect on sintering performance. In this paper, sinter pot tests were systematically conducted with various alumina types and contents by means of alumina additives substituting for the corresponding types of alumina, and the relevant action mechanism on sintering performance was clarified by the mineralogy of product sinter. The results show that kaolinite is beneficial to the granulation process rather than other three alumina types. In addition, it contributes to relatively better sintering performance while aluminous goethite ranks the only next, followed by gibbsite and free alumina. Mechanism analysis indicates that kaolinite and aluminous goethite are preferable to achieve relatively lower sinter porosity and higher amount of silico-ferrite of calcium and alumina (SFCA) compared with gibbsite and free alumina. Besides, the former two alumina types are apt to promote the formation of higher strength SFCA such as dendritic and acicular SFCA. Furthermore, much tighter interlocking texture in product sinter is formed as alumina occurs in kaolinite or aluminous goethite. Kaolinite and aluminous goethite are the preferably desirable alumina types for sintering rather than free alumina and gibbsite.

Multi-laser powder bed fusion (ML-PBF) has attracted much attention due to its advantage of directly building complex-structured and large-size components. In this work, this technique was conducted to fabricate Ti-6.5Al-2Zr-Mo-V (TA15) parts using sequential and synchronized scan strategies. The defect formation mechanism and the effect of the laser beam number (up to four) on density, microstructure, and microhardness were clarified. We find that the densification gradually deteriorates as increasing the number of involved laser beams. The laser-switching induced pores are dominated in the sequential scan strategy, which cause a directional pore distribution along the overlap lines. The synchronized scan strategy has a similar phenomenon. Moreover, the laser intersection induced by the synchronized scan strategy leads to a potential transition of molten pool mode and an increase of recoil pressure, which significantly deteriorates the densification. ML-PBF processed Ti-6.5Al-2Zr-Mo-V parts are composed of near-full acicular martensite α'. ML-PBF induces the low angle grain boundary to transfer to the high angle grain boundary due to the heat accumulation effect. Consequently, slow grain coarsening of acicular martensite α' occurs with more laser beams involving in. This leads to the microhardness of single-, dual-, and quadruple- L-PBF processed samples value from ~423 Hv to ~388 Hv. The microstructure-property correlation in ML-PBF is in good agreement with the Hall-Petch relationship.

The development of compressive residual stress is governed by the metallurgical transformation and associated microstructure, which in turn influences the mechanical properties of a welded structure. In the present work, the microstructural interaction with the thermo-mechanical performance of Yb-Fiber laser-welded austenitic stainless steel (SS304) is evaluated at different heat inputs and varying defocus distances. The interrelation between microstructural morphology and the typical pattern of residual stress is systematically investigated. The development of the thermal-metallurgical-mechanical model particularly considers the effect of solid-state phase transformation (SSPT) such that the model predicts the phase fraction and its influence on residual stress distribution. The present study exclusively focuses on the mechanism of residual stress generation as a consequence of dual-phase microstructural evolution during solidification. Low heat input (45 J/mm) leads to a high cooling rate, excellent tensile strength, and low tensile residual stress. The finite element-based thermo-mechanical model predicts the residual stress with a maximum deviation of ± 50 M P a compared to the experimental value. The Ferritic-austenitic (FA) mode of solidification results in the combination of skeletal and lathy δ -ferrite morphology. Increasing peak intensity of δ {110} with a cooling rate confirms the enhancement of δ -phase within the austenite matrix and restricts the complete transformation to the austenitic phase. A relatively high amount of δ -ferrite due to enriched Cr and lean Ni content at the dendritic core with fine or acicular morphology at a high cooling rate reduces the longitudinal and transverse residual stress significantly. Besides, the increasing trend of primary dendritic arm-size of δ -ferrite yields a gradual increase in residual stress.

Ti-5Al-2.5Sn alloy plates of 1.6 mm thickness were EB welded using four weld patterns (rectangular, elliptical, concentric circles and arrow). The fusion zone of all the patterns with variable amount had α´ martensite and acicular α with prior β at grain boundaries which resultantly affected the corrosion resistance. Several electrochemical techniques indicated that the elliptical pattern showed better passivation and film stability as compared to other patterns. The arrow pattern experienced more pitting due to the higher proportion of α´ martensite in its FZ. The EIS data indicated that the elliptical pattern had a stable uniform layer formation on the surface with low passivation resistance. In case of BM, uniform passivation layer of oxides was formed, without any sensitization.

O objetivo deste trabalho é analisar as propriedades mecânicas e microestrutural do processo automatizado de soldagem híbrida TIG- MAG. Os testes foram executados depositando cordões de solda sobre chapas de aço SAE 1020 com espessura de 1/4”. Foram realizados testes de dureza HRB, Charpy-V e análise microestrutural. Para os processos de soldagem, o MAG possuiu maior quantidade de energia absorvida no ensaio de Charpy-V e maior dureza HRB que os outros processos de acordo com os parâmetros adotados. A análise microestrutural possibilitou verificar a formação de uma estrutura parcialmente esferoidizada e o surgimento de ferrita acicular e primária.

Cardite, Zn5.5(AsO4)2(AsO3OH)(OH)3·3H2O, is a new secondary mineral from the Block 14 Opencut, Broken Hill, New South Wales, Australia. Cardite occurs as radiating sprays of acicular crystals to 0.09 mm in length associated with anglesite, pyromorphite and kottigite. The mineral is white to pinkish white and pale tan with a white streak. Crystals are translucent with a vitreous lustre. The tenacity is brittle and the fracture is uneven. The calculated density is 4.02 g/cm3. Electron microprobe analyses (WDS mode) gave ZnO 43.39, CdO 7.26, CoO 1.24, MnO 0.59, FeO 0.12, As2O5 38.84, SO3 0.20, H2O (calc) 9.97, total 101.61 wt%. The empirical formula calculated on the basis of 18 oxygen atoms is (Zn4.75,Cd0.50,Co0.15,Mn0.07,Fe0.01)5.48[(AsO4)2.01(SO4)0.02]2.03(AsO3OH)(OH)2.89·2.98H2O. Cardite is orthorhombic, Cmcm, with unit-cell dimensions (100 K): a = 15.110(3), b = 15.492(3), c = 6.3850(13) A, V = 1494.7(5) A3 and Z = 4. The eight strongest lines in the X-ray powder diffraction pattern are [d(A), (I), (hkl)]: 10.783 (100) (110), 7.564 (85) (200), 4.143 (48) (221), 3.328 (31) (041), 3.012 (20) (421), 2.763 (31) (222), 2.668 (24) (312), 2.451 (21) 260, 351, 461). The crystal structure of cardite (R1 = 0.067 for 13938 observed reflections with Fo > 4σ(Fo)) contains sheets of edge-sharing octahedra in which there is one vacancy for each four Zn cations in the sheet. Two orthogonal sheets lie parallel to (110) and to (1–10) and link along [001] by sharing common octahedra. AsO4 tetrahedra link to both sides of the sheet by corner-sharing. ZnO4 tetrahedra occupy channels in the structure and link to the sheets via corner-sharing AsO4 tetrahedra.

Motility is significant in organisms. Studying the influence of motility on biological processes provides a new angle in understanding the essence of life. Biomineralization is a representative process for organisms in forming functional materials. In the present study, we investigated the biomineralization of iron oxides templated by Escherichia coli (E. coli) cells under oscillation. The formation of iron oxide minerals with acicular and banded morphology was observed. The surface charge of E. coli cells contributed to the biomineralization process. The surface components of E. coli cells including lipids, carbohydrates and proteins also have roles in regulating the formation and morphology of iron oxide minerals. As-prepared mineralized iron oxide nanomaterials showed activity in photocatalytic degradation of methylene blue as well as in electrocatalytic hydrogen evolution reaction. This study is helpful not only in understanding motility in biological processes, but also in developing techniques for fabricating functional nanomaterials.