Powder Surface Research Articles

High Calorific Values Boron Powder: Ignition and Combustion Mechanism, Surface Modification Strategies and Properties

Boron powder is a kind of metal fuel with high gravimetric and volumetric calorific values, which has been widely used in military fields such as solid propellants, high-energy explosives, and pyrotechnics. However, the easily formed liquid oxide layer can adhere to the surface of boron powder and react with the hydroxyl (-OH) group of hydroxyl-terminated polybutadiene (HTPB) binder to form a gel layer that is detrimental to propellant processing and restricts the complete oxidation of boron powder. Therefore, to improve the combustion efficiency of boron powder, the ignition and combustion mechanisms of boron powder have been studied, and surface coating modification strategies have been developed by researchers worldwide, aiming to optimize the surface properties, improve the reaction activity, and promote the energy release of boron powder. In this review, recent studies on the ignition and combustion mechanisms of boron powder are discussed. Moreover, the reported boron powder coating materials are classified according to the chemical structure and reaction mechanism. Additionally, the mechanisms and characteristics of different coating materials are summarized, and the mechanism diagrams of fluoride and metal oxide are provided. Furthermore, promising directions for modification methods and the potential application prospects of boron powder are also proposed.

Effect of bamboo powder surface treatment on performance of asphalt binder

For expanding the application field of bamboo and improving the utilization rate of bamboo, the effect of bamboo powder (BP) treated by NaOH on the asphalt binder’s properties was discussed on the basis of previous study on the rheological property of bamboo powder modified asphalt at high temperature. The specific surface area, pore size distribution and pore structure of NaOH treated BP were analyzed by nitrogen adsorption experiment, and its micro morphology was explained by SEM. The high temperature stability, low temperature ductility, shear deformation resistance and rut resistance of BP asphalt binder were analyzed by the softening point, the ductility, the viscosity and dynamic shear rheological test. The results showed that under the treated by NaOH, the BP epidermis produced lamellar peeling, increased the specific surface area, the surface morphology was rougher, effectively improve the surface infiltration and physical adsorption capacity of BP and the asphalt binder. Both NaOH concentration and BP content increased would play positive roles on the asphalt binder’s properties, including the high temperature stability and shear deformation resistance. But the concentration and proportion should be moderate. It is suggested that 10% of BP treated with 2.5 mol/L NaOH concentration can obtain better performance of asphalt binder. By turning waste into treasure, the effective utilization of bamboo leftovers, which is a green environmental protection material, is realized, and the asphalt binder’s properties is significantly improved under the condition of simple process and low production cost.

Fabrication of graphene/Cu composites with in-situ grown graphene from solid carbon source

The high temperature melting and sintering of Cu powder will seriously limit the coverage of graphene on the surface of Cu powder during the in-situ generation of graphene. To solve this problem, MgO was added as a dispersant preventing Cu powders from bonding together due to surface melting during the chemical vapor deposition. The results show that the graphene/Cu powder prepared by this method had higher coverage, and the graphene/Cu composite sintered had better mechanical and anti-corrosion properties. It was attributed to the grain refinement strengthening effect and dislocation strengthening effect by the introduction of graphene. Meanwhile, graphene reduced the coverage of CuCl during Cl− corrosion. Therefore, this method provided a new idea for the preparation of high strength and high corrosion-resistant graphene/Cu composites.

A core-shell FeNiP@ SrFe-MOF magnetic powder with rapid and efficient degradation of dye and Cr(VI) wastewater

In this paper, a kind of zero valent FeNi alloy nano powder was coated on the surface of SrFe-MOF powder by a simple, efficient and pollution-free method, forming a core-shell type FeNip@SrFe-MOF Magnetic powder (FSM). The FSM powder has a porous structure and a specific surface area of 9.16 ​m2/g. Under normal temperature and without changing the pH value of the wastewater, the FSM magnetic powder has an immediate and efficient removal effect on Congo Red (CR) dye wastewater. Furthermore, the powder has good cycling performance, with the CR removal rate remaining above 90% after five cycles. Also at room temperature and without changing the pH value of the wastewater, the FSM magnetic powder provides some immediate, efficient, and repeated use degradation of Cr(VI) wastewater. The FSM magnetic powder has good magnetic properties so that can be easily separated and recovered by magnetic field treatment, which solves the problem of efficient recovery of raw materials in wastewater treatment. FSM magnetic powder has broad application prospects for treating wastewater.

Novel in-situ controllably grown CSH: Synthesis, characterization and the effect on cement hydration

CSH nanoparticles are distinctly different from other nano-additives because they are supposed to be ideal nucleation substrates for hydration products. One of the biggest obstacles is the difficulty in achieving a good dispersion of CSH nanoparticles in the matrix. We utilize a novel method to prepare composites by in-situ grown CSH nanoparticles (ICSH) on the surface of iron tailings powder (ITP) particles, and the growth amount and Ca/Si ratio of CSH can be precisely controlled. The results show that the agglomeration of CSH nanoparticles can be reduced by using the inert ITP admixture which is easy to disperse uniformly in cement-based materials. Studies on the properties of modified cement show that ICSH is significantly better than pure CSH powder in improving early hydration, pore structure and long-term compressive strength. These improvements are mainly attributed to the good dispersion of ICSH and the rigid system of the ITP matrix. This study provides theoretical guidance for improving the dispersion of nanoparticles in cement matrices.

Microstructure and Mechanical Properties of Y4Zr3O12-Added Fe-13.5Cr-2W Oxide-Dispersion-Strengthened Steels, Containing High Contents of C and N, Prepared by Mechanical Alloying and Two-Step Spark Plasma Sintering.

Oxide-dispersion-strengthened (ODS) steel is considered as a promising candidate structural material for nuclear applications. In this study, the microstructure and mechanical properties of Y4Zr3O12-added Fe-13.5Cr-2W ODS steels, containing high contents of C and N, prepared by mechanical alloying (MA) and two-step spark plasma sintering (SPS), were investigated. The results showed that pure Y4Zr3O12 powders, with a grain size of 3.5 nm, were well prepared with NH3·H2O addition by the sol-gel method in advance, in order to avoid the formation of some coarse or undesired oxides. W was completely dissolved into the matrix after 48 h of ball milling at 300 rpm, and the main elements were uniformly distributed on the surface of the milled powders. The unexpected face-centered cubic (FCC, γ)/body-centered cubic (BCC, α) dual-phase structure of the sintered specimens, could be explained by the unexpectedly high contents of C and N from the raw powder production process, fast-sintering characteristic of SPS, and inhibitory effect of W on the diffusion of C. The experimental results were approximately consistent with the simulation results from the Thermo Calc software. The temperature combination of 800 °C and 1100 °C during the SPS process, provided a relatively more homogeneous microstructure, while the combination of 750 °C and 1150 °C, provided the highest ultimate tensile strength (UTS), of 1038 MPa, with the highest uniform elongation (UE), of 6.2%. M23C6, Cr2O3, M2(C,N), and other precipitates, were mainly distributed at grain boundaries, especially at the triple junctions, which led to Cr depletion at grain boundaries.

Properties Optimization of Soft Magnetic Composites Based on the Amorphous Powders with Double Layer Inorganic Coating by Phosphating and Sodium Silicate Treatment

Core-shell structured amorphous FeSiBCr@phosphate/silica powders were prepared by phosphating and sodium silicate treatment. The soft magnetic composites (SMCs) were fabricated based on these powders. The effects of phosphoric acid (H3PO4) concentration and annealing temperature on their properties were investigated. During the phosphating process, the powder coated with a low concentration of H3PO4-ethanol solution leads to uneven phosphate coating, while the peeling of phosphate coating occurs for the high H3PO4 concentration. Using 0.5 wt.% phosphoric solution, a uniform and dense insulation layer can be formed on the surface of the powder, resulting in increased resistivity and the reduced eddy current loss of the amorphous soft magnetic composites (ASMCs). This insulation layer can increase the roughness of the powder surface, which is beneficial to the subsequent coating of sodium silicate. By optimizing sodium silicate treatment, a complete and uniform SiO2 layer can be formed on the phosphated powders well, leading to double layer core-shell structure and excellent soft magnetic properties. The magnetic properties of amorphous SMCs can be further improved by post annealing due to the effectively released residual stress. The enhanced permeability and greatly reduced core loss can be achieved by annealing at 773 K, but the deterioration of magnetic properties occurs as the annealing temperature over 798 K, mainly due to the increase of α-Fe(Si) and Fe3B phases, which hinder the domain wall displacement and magnetic moment rotation. The excellent soft magnetic properties with permeability μe = 35 and core loss Ps = 368 kW/m3 at 50 mT/200 kHz have been obtained when the SMCs prepared with the powders coated by 0.5 wt.% H3PO4 and 2 wt.% sodium silicate were annealed at 773 K.

Research on synthesis and property of nano-textured Sc2O3-MgO efficient antibacterial agents.

In order to obtain the inorganic efficient antibacterial agents, the means of ion doping and morphology construction in this research are used to enhance the antibacterial property of nano-MgO, which is according to the "oxidative damage mechanism" and "contact mechanism". In this work, the nano-textured Sc2O3-MgO are synthesized by doping Sc3+ in nano-MgO lattice through calcining at 600°C. When the Sc3+ content reaches 10%, the nanotextures on the powders surface are pretty clearly visible and uniform, and the specific surface area and the oxygen vacancy are ideal, so that the 10% Sc3+-doped powders (SM-10) has the excellent antibacterial property against E. coli and S. aureus (MBC = 0.03mg/mL). The efficient antibacterial agents in this research have a better antibacterial effect than the 0% Sc3+-doped powders (SM-0, MBC = 0.20mg/mL) and the commercial nano-MgO (CM, MBC = 0.40mg/mL), which have application prospects in the field of antibacterial.

Properties of Y<sub>2</sub>O<sub>3</sub> Dispersion Strengthened W Fabricated by Ultrasonic Spray Pyrolysis and Pressure Sintering

The effects of fabrication method on the microstructure and sinterability of W-1 wt% Y<sub>2</sub>O<sub>3</sub> were analyzed. W composite powders dispersed with Y<sub>2</sub>O<sub>3</sub> particles were synthesized by the ultrasonic spray pyrolysis process or the ultrasonic spray pyrolysis/polymer solution process. A dense composite was fabricated by a combination of spark plasma sintering and final hot isostatic pressing. The powder synthesized by the ultrasonic spray pyrolysis had fine dispersed particles on the surface of the cubic powder and was composed of W, Y<sub>2</sub>O<sub>3</sub> and W-oxides. On the other hand, in the case of the ultrasonic spray pyrolysis/polymer solution process, the nano-sized particles formed agglomerates and existed only as pure W and Y<sub>2</sub>O<sub>3</sub> phases. All the sintered compacts treated with HIP showed an increase in relative density, and the sintered compacts of the powder synthesized by the ultrasonic spray pyrolysis/polymer solution process showed a maximum relative density of 97~99% and a fine grain size. The change in microstructure with different powder processing was explained by the presence of W-oxide and the size and distribution of Y<sub>2</sub>O<sub>3</sub> particles. The Vickers hardness of the sintered compact reached the largest value of about 5 GPa in the powder synthesized by the ultrasonic spray pyrolysis/polymer solution process, which was interpreted to be a result of the relatively high density and decreased grain size.

Extracting particle size distribution from laser speckle with a physics-enhanced autocorrelation-based estimator (PEACE)

Extracting quantitative information about highly scattering surfaces from an imaging system is challenging because the phase of the scattered light undergoes multiple folds upon propagation, resulting in complex speckle patterns. One specific application is the drying of wet powders in the pharmaceutical industry, where quantifying the particle size distribution (PSD) is of particular interest. A non-invasive and real-time monitoring probe in the drying process is required, but there is no suitable candidate for this purpose. In this report, we develop a theoretical relationship from the PSD to the speckle image and describe a physics-enhanced autocorrelation-based estimator (PEACE) machine learning algorithm for speckle analysis to measure the PSD of a powder surface. This method solves both the forward and inverse problems together and enjoys increased interpretability, since the machine learning approximator is regularized by the physical law.

Experimental approach for development of a powder spreading metric in additive manufacturing

The powder spreading is a vital step of powder-based additive manufacturing (AM) processes. The quality of spread powder can considerably influence the properties of fabricated parts. Poorly packed powder beds with high surface roughness result in printed part layers with large porosity and low dimensional accuracy, leading to poor mechanical properties. Therefore, the powder spreadability and its dependence on process parameters and powder characteristics should be quantified to improve the efficiency of powder-based AM methods. This study proposes a novel dimensionless powder spreadability metric that can be commonly used in different powder-based AM processes. The quality of spread powder in terms of powder bed density and surface roughness was evaluated by adjusting the process parameters including recoating velocity and layer thickness, and powder characteristics including particle size distribution. In addition, the dynamic repose angle was proposed and examined as another powder spreadability metric. The results showed that these two proposed metrics were strongly correlated and lower recoating velocity and larger layer thickness led to higher spreadability and lower dynamic repose angle.

Study on inhibition of explosion of titanium powder by mesoporous calcium compound/carbonized chelating resin composite powder

In order to effectively inhibit the explosion of titanium powder, new mesoporous calcium compound/carbonized chelating resin composite powder was prepared in this paper using macroporous chelating resin as the substrate. The inhibition effect of mesoporous composite powder on the explosion pressure evolution and explosion flame spread of titanium powder was tested using Dust explosion test system and Hartmann experimental system, respectively. The experimental results show that when the addition ratio of mesoporous composite powder reaches 80%, the maximum pressure of titanium powder explosion is reduced to 0.259 MPa, and the explosion flame spread distance is reduced to 194.12 mm, which has an obvious inhibiting effect on titanium powder explosion. The results show that: mesoporous composite powder in a high-temperature environment, heat decomposition to generate a large number of calcium compounds, calcium compounds undergo chemical reactions consume a large number of radicals required for explosion reactions; while generating a large number of solid and gaseous substances, the formation of a dense carbon layer covering the surface of titanium powder to play a good barrier effect, and dilute the concentration of oxygen, further limiting the explosion reaction, with a good physical-chemical synergistic inhibition effect, to achieve a good effect of inhibiting the explosion of titanium powder. This study can make a contribution to the development of new explosion suppressing powder and the prevention and control of combustion and explosion accidents during industrial production; ultimately, it can realize the safe and orderly smooth production of enterprises involving combustible dust and gas.

Porous Material Made from Non-Firing Ceramics

The establishment of a carbon-neutral society has reached a stage when it is economically and industrially realistic. Based on this background, research on "non-firing ceramics" has attracted attention from the perspective of environmentally friendly manufacturing, such as energy conservation, low cost, and reduction of greenhouse gas emissions, because high temperatures and high pressures are not required. This technology involves a method to grind the surface of a ceramic raw material powder to obtain a chemical activity and solidify it. This paper provides an overview of non-firing ceramics, the mechanism of the surface activation of ceramic raw materials, and its application to porous materials. Although this method is not a substitute for all sintered ceramics, I hope that it will contribute to providing a new direction of manufacturing.

Carbonic anhydrase activity identified in the powdered nacreous layer of Pinctada fucata

The shells of Pinctada fucata are composed of CaCO3 and several organic molecules. The organic molecules containing chitin and proteins play a significant role in shell mineralization. Nacrein was the most abundant acid-soluble protein in the nacreous layer of P. fucata. Nacrein has a carbonic anhydrase (CA) domain that catalyzes the reversible conversion of CO2 to HCO3-. A nacre powder (NP) directly obtained from the crushed shells of P. fucata showed CA activity (Km=3.44 mM and kcat/Km=920 M−1 s−1). Furthermore, the powder was thermally stable at temperatures over 70 °C and was reusable after the 10th cycle of catalysis. Fluorescence detection showed that nacrein was exposed on the surface of the powder. This result suggested that nacrein was localized on the powder surface and provided CA activity to the powder. The shell of P. fucata is a readily available material because it is industrial waste in the pearl aquaculture. Recently, CA has attracted attention as a promising material for CO2 sequestration to mitigate global warming. We propose the use of NP as a reasonable and competitive biocatalyst for CO2 sequestration.

Research on the preparation of Ni/Al2O3 powder by fluidized crystallization granulation–hydrogen reduction

AbstractThis paper proposes a new process route for the preparation of Ni/Al2O3 composite powder through fluidized crystallization granulation–hydrogen reduction and investigates the effects of process feasibility, nickel concentration, nucleation method, and hydrogen reduction on Ni/Al2O3‐coated powder. The decrease in nickel concentration, heterogeneous nucleation, and natural air‐drying properties of precursor particles was beneficial to the formation of a complete and uniform cladding layer, and the increase in hydraulic retention time could improve the thickness of the cladding layer. The optimum process involves a nickel concentration of 50 mg/L; hydraulic residence time of 75 h to ensure heterogeneous nucleation; two‐step hydrogen reduction of precursor particles to obtain a complete and uniform Ni/Al2O3 cladding layer; and a powder surface nickel content of 59.5%.

High stability of solid electrolyte interphase in lithium metal batteries enabled by direct fluorination on metal iron powder

Multiple studies attempted mixing Li with microparticle metal powders or using it to impregnate a porous media to utilize for thermal batteries. The infusion of Li into porous structures or powders is challenging as most materials used in battery fabrication are lithiophobic to molten Li. Optimizing and improving the wettability of molten Li is one approach to address this. Herein, we propose an efficient and facile direct fluorination method for achieving an ultra-lithiophilic fluoride layer on the surface of a Fe powder. Fluorination of Fe powders resulted in a significant increase in the wettability of molten Li by growing a Fe-F layer on the surface of the Fe powder. This layer was lithiophilic and showed good wettability. An anode prepared using fluorinated Fe-Li metal showed no evidence of short circuits or dendrite formation after a cycle test at 0.2 mA cm−2. Both a pure Li anode and pristine Fe powder showed unstable charge–discharge characteristics when used as an anode in cycle tests. This proposed method will further develop rechargeable lithium-metal battery technology.

Dispersion of in-situ controllably grown nano-SiO2 in alkaline environment for improving cement paste

Nano-SiO2 (NS) has attracted considerable cementitious interest due to the new potential uses of nanoparticles. However, the dispersion problem of NS in alkaline cement environments has restricted its real application. Therefore, in situ-grown NS (INS) on the surface of iron tailings powder (ITP) can also be uniformly dispersed in the cement-based material by taking advantage of the inert ITP admixture's property of being easily and uniformly dispersed in the cement, simultaneously effectively controlling the particle size and the amount of growth of NS. To this end, the characteristics and dispersion stability of INS were evaluated by TEM, SEM, FTIR, XRD and other characterization methods, and the results showed that an amorphous nano-silica layer can be uniformly adsorbed on the surface of ITP, which was conducive to effectively decreasing the aggregation of NS. Compared with commercial NS, INS can better promote cement hydration and reduce the moisture wrapped by NS agglomerates, thus maintaining a good fresh property, and INS can also improve the early and long-term compressive strength of cement pastes. Moreover, the hydration reaction and microstructural evolution were evaluated and comparison with commercial NS through isothermal calorimetry, XRD, TG/DTG, NMR, MIP and BSEM analyses. This work has opened a new strategy to develop NS as a nano reinforcing material for cement composites.

Enhancing soft magnetic properties of FeSiBNbCu nanocrystalline powder cores by coating ZrO2 insulation layer

The insulation coating plays a crucial role in minimizing core loss (Pcv) in soft magnetic powder cores (SMPCs). In this work, we prepared ZrO2 coating layer on FeSiBNbCu spherical powder by the hydrolysis-precipitation method and investigated the magnetic properties of the FeSiBNbCu@ZrO2 nanocrystalline SMPCs. ZrO2 coating layer were successfully fabricated on the powder by adding a proper amount of K2ZrF6 in alkaline ethyl alcohol solution. The micromorphology and chemical structure of the ZrO2 coating layer on the surface of FeSiBNbCu nanocrystalline powder, as well as the conversion mechanisms, has been investigated. The presence of the ZrO2 coating reduces the Pcv by significantly lowers eddy loss (Pe) of the nanocrystalline SMPCs, meanwhile improves DC bias performance and slightly decreases their permeability. When the additive amount of K2ZrF6 is 1.0 wt%, the nanocrystalline SMPCs has best comprehensive soft magnetic properties, including stable effective permeability (μe) of 57.8 up to 1 MHz, excellent DC bias performance of 59.3 % at a bias field of 100 Oe, and the lowest Pcv of 194.7 mW/cm3 at a frequency (f) of 150 kHz and maximum magnetic induction (Bm) of 50 mT.

Combined effect of a spread powder particle size distribution, surface machining and stress-relief heat treatment on microstructure, tensile and fatigue properties of 316L steel manufactured by laser powder bed fusion

Combined effect of a spread powder particle size distribution, surface machining and stress-relief heat treatment on microstructure, tensile and fatigue properties of 316L steel manufactured by laser powder bed fusion

Thin superhydrophobic layers on the SiC powder surface toward electrical erosion resistance

Thin superhydrophobic layers on the SiC powder surface toward electrical erosion resistance