Degree Of Pulverization Research Articles

Microstructural Investigation of Discarded NdFeB Magnets After Low-Temperature Hydrogenation

Due to continuously increasing demand and limited resources of rare-earth elements (REEs), new solutions are being sought to overcome the supply risk of REEs. To mitigate the supply risk of REEs, much attention has recently been paid to recycling. Despite the more common recycling methods, including hydrometallurgical and pyrometallurgical processes, hydrogen processing of magnetic scrap (HPMS) is still in the development stage. Magnet-to-magnet recycling via hydrogenation of discarded NdFeB magnets provides a fine powder suitable for the production of new magnets from secondary sources. One of the crucial aspects of HPMS is the degree of recovery of the magnetic properties, as the yield efficiency can easily reach over 95%. The amount, morphology, and distribution of the Nd-rich phase are the key parameters to achieve the excellent performance of the magnet by isolating the matrix grain. Therefore, a better insight into the microstructure of the matrix grains and the Nd-rich phase before and after hydrogenation is essential. In this study, a low-temperature hydrogenation process in the range of room temperature to 400 °C was conducted as the first step to recycle NdFeB magnets from discarded hard disk drives (HDDs), and the hydrogenated powder was characterized by electron microscopy and X-ray diffraction. The results show that there are three different morphologies of the Nd-rich phase, which undergo two different transformations through oxidation and hydride formation. While at lower temperatures (below 250 °C) the degree of pulverization is higher and the experimental evidence of hydride formation is less clear, at higher temperatures the degree of pulverization decreases. The formation of neodymium hydride at higher temperatures prevents further oxidation of the Nd-rich phase due to its high stability.Graphical

Technology and Peculiarities of Production of Large-format Ceramic Stones Based on Opoka-like Rocks

Introduction. One of the urgent tasks of the wall ceramics industry at present is the production of large-format ceramic stones with compressive strength of 10–15 MPa and thermal conductivity less than 0.12 W/(m·оС), while the market cost per 1 m3 should be competitive with gas-concrete blocks and be in the range of 5–6 thousand rubles per 1 m3. This problem can be solved by developing modern energy-efficient production technology and using opoko-like rocks and coal processing wastes as the main raw material as fuel and burnout additive.Materials and Methods. The opoka-like rocks — opokas from the deposits of southern Russia — Nagolnovskoye, Bakanskoye, Shakhtinskoye, Avilo-Fyodorovskoye, and coal cake produced by Pyramida LLC were used for research. The study of chemical and mineral composition was carried out by standard methods on prepared samples. The study of ceramic and technological properties (plasticity, molding moisture, degree of crushing, air and fire shrinkage, compressive strength, water absorption) of raw materials was carried out according to generally accepted methods on samples precrushed to a certain grain composition, since opokas, depending on the type, do not soak or slowly soak in water.Results. Pre-firing technological properties of opokas and their differences from traditional clay raw materials soaked in water were confirmed: increased molding moisture, small air shrinkage, low sensitivity to drying. The dependence of density and strength of samples on the degree of pulverization of opoka, firing temperature and the amount of carbon cake in the raw material mixture has been established. The influence of coal preparation wastes and their optimal amount on physical and mechanical properties of fired samples has been determined. The introduction of carbon cake allows to exclude the use of gas for firing or minimize its introduction. On the basis of the obtained results a simplified technological scheme for the production of large-format stones with minimum production cost has been developed.Discussion and Conclusion. The proposed technological scheme consists of two units of the main mass preparation equipment, molding of products is carried out by semi-rigid extrusion, drying of products is carried out directly on kiln cars, and for firing coal cake is used, which is introduced into the raw mix. These factors and technological methods allow to obtain products with low thermal conductivity, but with strength 3–5 times higher than that of aerated concrete blocks of similar density. The prime cost of ceramic stones will amount to 3–3.5 thousand rubles per 1 m3 of products. Rostov region, possessing opoka-like rocks and unclaimed reserves of technogenic coal raw materials, can become a center of production of large-format ceramic stones with low cost and provide the south and central part of the country with highquality wall materials.

Preparation of Formed Coke from Biomass by Sequence of Torrefaction, Binderless Hot Briquetting and Carbonization

This paper proposes a method of preparing high-strength formed coke from woody biomass without binder. Chipped and pre-dried Japanese cedar was heat-treated in an inert atmosphere (i.e., torrefied) at 225–325°C (Tt), pulverized to sizes in three different ranges, molded into briquettes (in the form of thick disk with diameter/thickness ≈ 2.5) at temperature up to 200°C by applying mechanical pressure of 128 MPa. The torrefied/briquetted cedar (TBC) was then converted into coke by heating to 1000°C in an inert atmosphere at normal pressure. This process sequence enabled to prepare coke having indirect tensile strength (St) of 8–32 MPa, which was much higher than that without torrefaction, below 5 MPa. The torrefaction greatly improved pulverizability of the cedar, which was further promoted by increasing Tt. St of TBC and that of coke both increased as the particle sizes of TBC decreased, but this explained only a minor part of significant effect of Tt on St of the coke. St was maximized at Tt = 275°C regardless of the degree of pulverization. The Tt effects on physicochemical properties of TBC and coke were investigated in detail. The difference in St of coke by Tt was mainly due to that in the increment of St along the carbonization at 500–1000°C. Fracture surfaces of the coke had particular morphologies that had been inherited from the original honeycomb structure of the cedar.

Effect of Post-Added Water Amount on Pre-Concentrated Bark Foaming Materials by Mechanical Stirring

In this study, pre-concentrated bark, furfuryl alcohol and other biomass raw materials were used to prepare foaming materials by high-speed mechanical stirring without using a foaming agent. We investigated the effect of the postadded water amount on the properties of foaming materials. In particular, we determined basic physical properties of these materials, including the limiting oxygen index (LOI), porosity, thermal conductivity, thermogravimetric analysis, pore size distribution, and microstructure. The results of scanning electron microscopy (SEM) indicated that the pore size distribution was uniform and the pore size increased with increasing water volume. Thermogravimetric analysis (TG/ DTG) showed that when the temperature reached 410°C, the foam was easily decomposed, the final residual mass was only 2.8%, and water addition had little effect on it. Moreover, the amount of post-added water is 5–30 g, the density and compression strength of the foamed materials gradually decreased, while the degree of pulverization increased. LOI ranged from 26.1% to 30.79%, and porosity ranged from 81% to 83%. The change in water volume greatly affected the foam’s performance, the performance of foamed material deteriorated as the amount of added water increased, but the effect on thermal conductivity was not very obvious. The highest thermal conductivity was only 0.0179 W/(m·K), still providing excellent thermal insulation.

Numerical analysis on pulverization and self-densification for hydrogen storage performance of a metal hydride tank

High and steady hydrogen absorption/desorption rates are essential for long-term services in the field of hydrogen energy. However, the absorption/desorption rates will be affected by the changes of heat and mass transfer characteristics caused by pulverization and self-densification phenomena. In this work, a novel simplified numerical model is proposed for describing the effects of pulverization and self-densification on hydrogen storage performance in a Ti0.98Zr0.02V0.43Fe0.09Cr0.05Mn1.5 (HWT5800) metal hydride tank. The model is conducted using the finite element method under different degrees of pulverization and self-densification, from which the results agree well with the experimental data in literatures. The hydrogen absorption rate will be enhanced after pulverization of particles due to the increased reaction rate constant. The hydrogen absorption time at 80% of maximum hydrogen capacity (t80%) can be shortened from 2191.98 to 1797.23 s when particle radius ratio (PR) is 0.2. The hydrogen absorption rate will be reduced after self-densification, which is mainly attributed to the lower thermal diffusivity. t80% can increase from 1851.26 to 2304.54 s after self-densification, when the porosity at the top and bottom of MH bed is 0.7 and 0.3, respectively.

Effect of microstructure on the breakage of tin bronze machining chips during pulverization via jet milling

In this study, jet milling was used to recycle tin bronze machining chips into powder. The main purpose of this study was to assess the effect of the microstructure of tin bronze machining chips on their breakage behavior. An experimental target jet mill was used to pulverize machining chips of three different tin bronze alloys containing 7wt%, 10wt%, and 12wt% of tin. Optical and electron microscopy, as well as sieve analysis, were used to follow the trend of pulverization. Each alloy exhibited a distinct rate of size reduction, particle size distribution, and fracture surface appearance. The results showed that the degree of pulverization substantially increased with increasing tin content. This behavior was attributed to the higher number of machining cracks as well as the increased volume fraction of brittle δ phase in the alloys with higher tin contents. The δ phase was observed to strongly influence the creation of machining cracks as well as the nucleation and propagation of cracks during jet milling. In addition, a direct relationship was observed between the mean δ-phase spacing and the mean size of the jet-milled product; i.e., a decrease in the δ-phase spacing resulted in smaller particles.

An effect of screw-disc extrusion process on the level of WPC composites microbiological contamination

The article presents the results of an analysis of the effect of the screw-disc extrusion process on the microbiological quality of WPC composites. The research material consisted of components used for the manufacture of wood-plastic composites in a form of flour, and chips from two kinds of trees (deciduous and coniferous), as well as the PP granulate and composites obtained from them. The study was conducted in two stages. Stage I involved determining the microbiological contamination level in the components used for wood-plastic composite manufacturing. Stage II involved an examination of the microbiological purity of the final composites. The composites under examination were in two forms, i.e. rods and plates. The composites were obtained using a screw-disc extruder and molds for plate compression. The microbiological examinations were conducted according to the standard PN-EN ISO 21527-1:2009. It was observed as a result of the analysis performed that the wood waste used for the production of wood-plastic composites demonstrated strong microbiological contamination, unlike the original polymer material used in the composites matrix. Irrespective of the kinds and forms of the chips used (tree species, degree of pulverization and share), the applied extrusion parameters (temperature and pressure) caused the sterilization of the obtained composites. It may be concluded that the problems presented in the literature, related to an occurrence of molds and fungi on WPC elements used outside, are the result of secondary contamination.

Design and development of power-operated continuous-run potting machine for seedling-nursery

Potting is still a manual operation in plantation, forestry, and 11 other horticultural nurseries in India and the preparation of pot-mixture and filling in polybags are crucial tasks and are time consuming. Therefore, a poweroperated continuous-run machine was specially designed, fabricated, and tested to master seedling-nursery management capable of mixing, pulverizing, sieving, and filling of pot ingredients in polybags. The machine is a vertical freestanding unit mounted on four legs and consists of 3-hp motor, feed-hopper, pulverizing chamber with 8-numbers of paddles, sieving compartment operated by a slider-crank mechanism, vending instrumentation, and outlet. Ingredients like soil, sand, granite power, farmyard manure, and compost are fed from the top and the pot-mixture is collected at the bottom. Electronic vending is the novelty of the machine, which permits filling pot-mixture at set quantity at set time-gap. Aggregate analysis, degree of pulverization, and other physical parameters of machine-made mixture are at recommended level as well as on par with manually-made pot-mixture. More proportion (81.8%) of desirable level of aggregate was achieved with machine compared in manual method (79.5%) resulted in improved quality of the mixture for seedling establishment. Bagging through machine worked out 71.4% cost-saving and 80.2% time-saving. The machine is recommended for nursery-holders around the nation since the machine can provide pot-mixture for development of saplings of 30 000 numbers per month in a commercial nursery.

An Assessment of the Fuel Pulverization Threshold During LOCA-Type Temperature Transients

To investigate the potential disintegration to powder of high-burnup fuel pellets during a rapid temperature transient, the Nuclear Fuels Industry Research (NFIR) Program commissioned two independent scoping studies. The first investigated the effect of hydrostatic restraint pressure on fission gas release during a series of fast temperature ramps. In the second study laser heating was used to investigate the temperature at which small samples of fuel fragmented. From the observations made in these studies, local burnup and temperature thresholds of 71 MWd/kg HM and 645°C were identified for fuel pulverization during a loss-of-coolant accident (LOCA). It is shown that fine fragment production in integral LOCA tests performed in other independent investigations at Studsvik and Halden was generally well predicted using these thresholds of burnup and temperature. The NFIR investigations also reveal that the degree of pulverization and resulting fragment size are dependent on the temperature ramp rate. Moreover, they confirm that pulverization can be substantially reduced by the imposition of hydrostatic pressure.

Mn in misch-metal based superlattice metal hydride alloy – Part 2 Ni/MH battery performance and failure mechanism

The performance and failure mode of Ni/MH batteries made from a series of Mn-modified A2B7 superlattice and a commercially available AB5 metal hydride alloys were studied and reported. Cells with the Mn-free A2B7 alloy generally show improved low-temperature, higher peak power, and similar charge-retention behavior over those with a conventional AB5 alloy. As Mn-additive amount increased, cell voltage and high-rate capacity improved, low temperature, charge retention, and cycle life first improved, but then deteriorated, and peak power and high temperature voltage stand deteriorated. Analysis of battery performance test results show the use of a superlattice alloy containing 2.3% Mn as the best overall alloy composition. Failure analysis of the highly cycled AB5 alloy containing cells indicate a balanced degradation in negative, positive, separator, and a moderate loss of electrolyte. Same analysis on cells containing the various superlattice alloys suffered from a high degree of pulverization and oxidation of its negative electrode (with the 9.3% Mn content experiencing the worst amount of pulverization/oxidation) and a high degree of electrolyte loss.

Research on the Extraction of Dendranthema Morifolium Volatile Oils by Microwave-Assisted Steam Distillation Extraction

Microwave-assisted steam extraction system combines the advantages of both conventional and modern technologies. MAE is probably going to be the leading technology in essential oil producing industry. In our research, one-factor and uniform experimental designs are used to determine the optimum extraction conditions, and the results are as follows: the extraction yield is measured as 2.30% with 3h of reflux time, when degree of pulverization is 90, immersing time is 3h, yield of solid to liquid equals 12: 1 ml/g. The chemicals in the production were examined by GC-MS. More than 40 kinds of chemicals were detected, which is consistent with that of the traditional steam extraction method. However, the extraction efficiency is dramatically increased when the steam extraction is assisted with microwave heating, and it is up to 3.8 times.

Study on phenolic resin foam modified by montmorillonite and carbon fibers

In this article, phenolic resin was modified by montmorillonite(MMT) carbon fiber and other addition agents. This composite phenolic foam was characterized by XRD, SEM, and TEM the mechanical properties of this composite foam were measured as well. The results show that exfoliated phenolic resin/montmorillonite nanocomposites are obtained from acidulated montmorillonite (H-MMT) and phenolic resin by in-suit polymerization, the thickness of MMT layers is about 20-40nm, and the affinity between the MMT and phenolic resin is very good. During the forming of phenolic foams, because of the inflation of bubbles and the streching of bubble walls, MMT layers possess a certain orientation in this composite foam, forming a structure in which bubbles are wrapped around by MMT layers. So the degree of pulverization is decreased, and the compressive strength of this foam is increased by 35%-40%. Besides, MMT layers dispersed in this foam contribute greatly to its antiflaming and better properties. However, when the content of H-MMT is above 7%, MMT agglomeration appears. On the other hand, when carbon fibers are added to phenolic resin as a crosslink, they can prevent cracks from developing. Due to the excellent mechanical property and thermostability of carbon fibers, the flexural strength is increased by 58%, and the carbon yield ratio of composite foam is improved by no less than 8% when it is heated to over 500°C.

Pulverized fault rocks and damage asymmetry along the Arima-Takatsuki Tectonic Line, Japan

We present field and laboratory data on pulverized rocks at the Hakusui-kyo outcrop of the Arima-Takatsuki Tectonic Line (ATTL), which is a dextral strike slip fault with ~ 17 km displacement juxtaposing granite to the south against rhyolite to the north. The majority of slip at the surface is localized to a clay-rich gouge fault core 8–10 cm in width, surrounded by a coarsening outwards fault breccias up to 3 m wide. Fault damage is highly asymmetric with respect to the slipping zone. The granite south of the fault has a pulverized damage zone up to 200 m wide, while the rhyolite to the north has only about 3 m wide non-pulverized fault breccia. The degree of pulverization in the granite decreases approximately logarithmically with normal distance from the slip zone. The highly fractured pulverized rocks exhibit several distinct textural characteristics. In thin section, grains appear to be highly comminuted but the original grain shapes and margins are recognizable. Microfractures tend to be tensile in no preferred orientation. Grain fragments display little to no rotation and lack evidence of in-situ shear. Consequently, at macroscale the rocks appear to preserve original granitic textures, despite being highly fractured and friable. The observed pulverization and rock damage asymmetry are most consistent with generation mechanism involving ruptures on a bimaterial interface with statistically preferred propagation direction, leading to damage primarily on the side with higher seismic velocity at depth. This is supported by laboratory measurements of P-wave ultrasonic velocities on intact samples which indicate that the granites have consistently higher velocity than the rhyolite with increasing confining pressure.

In Situ Fabrication of Surface Modified Lead Monoxide Nanopowder and Its HDPE Nanocomposite

Low density polyethylene (LDPE) coated lead monoxide (PbO) nanopowder was fabricated by using in situ high energy wet ball milling. Degrees of pulverization of wet milled PbO together with LDPE and cyclohexane were analyzed by means of PSA and SEM. PbO powder could be pulverized to ∼100 nm for 1 h milling while the surfaces of the powder particles were modified with LDPE simultaneously. Surface modification by elemental interdiffusion of PbO and carbon on the particulate boundary was confirmed by TEM/EDX. High density polyethylene (HDPE) nanocomposites were also prepared by dispersing micro- and nano-PbO/LDPE powders using a polymer melting mixer. Dispersion and adhesion of PbO/LDPE nanoparticles in or with the polymer matrix were homogeneous and strong respectively according to the SEM images as well as the FTIR spectra, while the HDPE nanocomposites show higher mechanical properties than those for micro-PbO powder dispersed ones.

Pressure–composition–temperature hysteresis in C14 Laves phase alloys: Part 1. Simple ternary alloys

In Part 1 of a series of two papers, the a/ c lattice constant ratio of ZrCr 2-based ternary alloys are shown to be strongly correlated not only to the number of outside electrons of substitutional elements but also to the PCT absorption/desorption hysteresis and the degree of pulverization during hydride/dehydride cycling of the alloy. In differentiation from AB5 alloys in which elongating the c-axis dimension of the unit cell extends the alloy's electrochemical cycle life, flattening the unit cell of an AB2 alloy extends its cycle life. This difference can be explained by the different hydrogen occlusion sites of the two structures. Adding small amounts (10%) of substituents such as Zn, Cr, Mo, Si, or Cu, was generally found to help the prevention of the alloy hydride/dehydride pulverization by maintaining a relatively high a/ c lattice constant ratio. Application of these principles to more complicated electrochemical hydrogen storage alloys can be found in Part 2 of this series.

Pressure–composition–temperature hysteresis in C14 Laves phase alloys: Part 2. Applications in NiMH batteries

This part of our series of papers reports our efforts to predict sealed cell cycle life from lattice constant a/ c ratio and/or PCT hysteresis based on correlations established from our previous studies reported in Part 1. In the case of Ti 21Zr 12.5V 14Ni 21.5− x Cr 10Mn 21Sn x alloys, as x is increased the a/ c ratio increases and the PCT hysteresis decreases resulting in extended cycle life for the battery. This is in agreement with the results from Part 1. In the case of Ti 18Zr 15.5V 14Ni 24.2− x Cr 10Mn 18− y Sn 0.3Co x Al y alloys, the a/ c ratio trend was not observed due to existence of more than one C14 phase, but the correlation between PCT hysteresis and cycle life was maintained. In the case of Ti 21Zr 12.5V 10Ni 40.2Cr 8.5− x Mn 5.6− y Co 1.5+ x+ y Al 0.4Sn 0.3 alloys, the cycle life was dominated by the corrosive nature of the alloy affected by the Cr content. As a consequence, predictions from a/ c ratio and PCT hysteresis can only be applied to the degree of pulverization in gas phase cycling and not to the sealed cell cycle life.

Influence of rapid quenching on the microstructure and electrochemical properties of Co-free [formula omitted] hydrogen storage electrode alloy

Co-free LaNi 4.92 Sn 0.33 alloy samples were prepared by first induction melting and subsequent melt-spinning at different quenching rates, and their microstructure and electrochemical properties were comparatively investigated and compared. The results reveal that the as-cast alloy is of a coarse dendrite structure consisting of two distinct CaCu 5 major phases and a scattered minor Sn phase, has high volume expansion and pulverization rates on hydriding and noticeable composition segregation, resulting in a rather poor cycling stability ( S 200 = 42.7 % ). However, the melt-spun alloys prepared at higher quenching rates are highly homogeneous in composition, of the single CaCu 5 phase in very fine cellular structure, have lower volume expansion and pulverization rates on hydriding, leading to a noticeably improved cyclic stability ( S 200 = 62.5 – 78 % ), although their activation rate, initial capacity and high-rate dischargeability are slightly lowered. It is believed that the great improvement in cycling stability of the melt-spun alloys is mainly due to their lower degree of pulverization on hydriding and the higher uniformity in composition, and the relatively lower high-rate dischargeability is mainly due to the decrease in both the electrocatalytic activity and the hydrogen diffusion rate in the alloy bulk.

활석 미분말의 콘크리트용 혼화재료로써 활용가능성에 관한 연구

Admixture materials are used in mixing concrete or mortar to improve quality and performance of the concrete. This study examines the potential use of talc as a substitute for cement, the benefits of recycling waste resources for economical efficiency and quality improvement of concrete. The test was carried out by replacing the plain mix with fine grains of talc at the rate of 10%, 20%, and 30%. Talc was divided into three groups depending on the degree of pulverizing. For wet concrete, porosity, slump, bleeding per unit, and setting time by penetration resistance were measured; similarly, for dry concrete, strength and watertight Property were tested. Test results showed that the amount of bleeding and setting time could be shortened, but the strength and watertight proofing severely deteriorated. However, at the replacement rate of 10%, talc showed equal performance with the plain at all degrees of pulverization, which suggests its potential use as admixture material.

Influence of the material processing on the electrochemical properties of cobalt-free Ml(NiMnAlFe) 5 alloy

Co-free MlNi 4.1Mn 0.35Al 0.3Fe 0.25 (Ml: La-rich mischmetal) alloy samples were prepared in three different ways. The original as-cast alloy was prepared by vacuum levitation melting in a cold crucible. One-third of the as-cast ingot was annealed at 1273 K for 10 h, and another one-third was remelted and rapidly solidified by melt-spinning. The influence of the alloy preparation methods on their microstructure and electrochemical properties was studied. XRD and SEM results revealed that all of the three differently prepared alloys were of the single CaCu 5-type structure phase, but their microstructure and electrochemical properties were changed markedly. The as-cast alloy had a typical dendrite structure with noticeable composition segregation and rather poor cycling endurance. While the annealed and melt-spun alloy were of an equiaxed structure and a very fine cellular structure, respectively, and had a more homogeneous composition and dramatically improved cycling endurance, although their activation rate and high-rate dischargeability were lowered somewhat. In this study, the melt-spun Co-free alloy showed the best cycling stability ( S 500=69.2%) and a reasonably high capacity (305 mA h g −1) and 1C rate dischargeability (85.6%), which is attributed to its lower degree of pulverization and more uniform composition.

Application of steady state maximum entropy methods to high kinetic energy impacts on ceramic targets

Summary The maximum entropy method is used to investigate the fragmentation and pulverization of ceramics subjected to high energy impacts. Since the exact physical processes that occur during high energy impacts on ceramic targets is not completely known, the calculation of the details of these interactions can at best be approximate. However, many of the general features of what will happen are known, such as conservation of energy-momentum and thermodynamic laws act as constraints on any model. The maximum entropy incorporates by the method of constraints everything known to be correct into the model. The more constrained the system, the better the model. Several important developments arise: It is important that the ceramic be confined long enough for the ceramic to be pulverized; and there will be, in general, a lower bound on the minimal size of the pulverized ceramics consistent with the properties of the ceramic and the kinetic energy of the penetrator. A sample application for a steady state erosion process due to the abrasive ceramic powder acting on the penetrator is discussed. The transfer of energy-momentum from the penetrator to the ceramic is shown to depend on the degree of pulverization and characteristic frequency associated with the impact event. Improvements and future directions for study are described in the conclusions.