Solid Transformation Research Articles

Finite element analysis of temperature and stress fields during selective laser melting process of Al–Mg–Sc–Zr alloy

A 3D finite element model was established to investigate the temperature and stress fields during the selective laser melting process of Al–Mg–Sc–Zr alloy. By considering the powder–solid transformation, temperature- dependent thermal properties, latent heat of phase transformations and molten pool convection, the effects of laser power, point distance and hatch spacing on the temperature distribution, molten pool dimensions and residual stress distribution were investigated. Then, the effects of laser power, point distance and hatch spacing on the microstructure, density and hardness of the alloy were studied by the experimental method. The results show that the molten pool size gradually increases as the laser power increases and the point distance and hatch spacing decrease. The residual stress mainly concentrates in the middle of the first scanning track and the beginning and end of each scanning track. Experimental results demonstrate the accuracy of the model. The density of the samples tends to increase and then decrease with increasing laser power and decreasing point distance and hatch spacing. The optimum process parameters are laser power of 325–375 W, point distance of 80–100 μm and hatch spacing of 80 μm.

Evaluation of phase change plaster/paste composites for building envelopes

Thermal energy storage (TES) materials increase a building’s thermal mass and provide the flexibility to shave and time-shift energy use. These materials are needed to enable grid-interactive efficient buildings, allowing building occupants to lower costs by leveraging free ambient heating/cooling as well as shifting consumption to cheaper electricity periods. Phase change materials (PCMs) that store heat through a solid–liquid/solid–solid transformation are of particular interest for TES because of their ability to store large amounts of energy across a constant temperature or very small temperature range. Previous studies on PCM building envelopes evaluated products that may only be incorporated as part of new construction and are not easily applicable to existing, energy-intensive buildings. In this work, we leverage laboratory PCM characterization and whole-building energy simulation to study the energy and cost savings of PCM plaster/paste coatings, which can be applied post construction to both new builds and retrofits of existing buildings (about 40% of residential buildings in the United States fall into the retrofit category). We evaluated the energy impact of PCM plaster/paste composites for a single-family residential building in the United States, including layer design (location and thickness), composite properties (phase change temperature, energy density, and shape of the enthalpy curve), and U.S. climate zone. The enthalpy curve shape of PCM shows that phase change temperature and energy density are not the only two parameters that must be considered for PCM selection. Maximizing the energy density amid the effective TES zone is key to boosting energy savings. We also studied PCM price targets with the aim of achieving reasonable payback periods based on both block and time-of-use electricity rates. Moreover, we developed an empirical equation to provide a rough estimate of the energy savings potential of incorporating PCM without the need to perform detailed simulations. These results will help guide the selection and design of PCM plaster/paste composite elements for residential building envelopes.

Comments on “Solubility measurement and correlation for HNIW·TNT co-crystal in nine pure solvents from t = (283.15 to 318.15) K”

The study by Jia et al. about solubility measurement and correlation of 2,4,6,8,10,12-Hexanitrohexaazaisowurtzitane ·2,4,6-trinitrotoluene (HNIW·TNT) co-crystal in nine pure solvents from 283.15 K to 318.15 K has been discussed from viewpoint of the determination of co-crystal thermodynamic solubility, solid transformations of excess solid and solution stability of co-crystal.

Efficient fabrication of metal sulfides/graphite anode materials derived from spent lithium-ion batteries by gas sulfidation process

Although regeneration of spent lithium-ion batteries is of great significance for alleviating resource-shortage and addressing environment issues, the recycling process still confronts with great challenges. Meanwhile, majority of recycling processes concentrate on the cathode materials, while the anode material has received little attention because of its low value. In this study, we develop a novel recycling process for spent LiNixCoyMn1-x-yO2/LiNixCoyAl1-x-yO2/graphite materials to prepare carbon–metal sulfides composites (NCMS/C and NCAS/C) by the gas sulfidation method. During this regeneration process, it can not only fulfill the efficient recycling within a short procedure of solid–solid transformation without involving tedious acid–base neutralization reaction, but also realize the recycling of high-valued components within the spent batteries simultaneously. Benefiting from the synergistic effect of the tight contact between metal sulfides and reconstructed graphite with high conductivity, it delivers the outstanding electrochemical properties for lithium storage (NCMS/C: 900.4 mAh g−1 at 0.2 A g−1 after 200 cycles, NCAS/C: 830.5 mAh g−1 at 0.2 A g−1 after 200 cycles). It is noted that this approach provides a new insight into the transformation from spent lithium-ion batteries to value-added materials with efficient reutilization, which makes full use of the valuable components by recycling spent cathode and anode materials synchronously, to achieve the win-win situation of environment protection and resource conservation.

Nicolaus Steno on solutes and solvents in time-related structural changes of muscles, fossils, landscapes and crystals, his galilean heritage

In Part One of the Specimen of Elements of Myology, a book in three parts published in Florence 1667, Nicolaus Steno described the changes taking place between muscle relaxation and contraction in a two-stage geometrical model based on anatomical observations in man and animals. The ‘new myology’ was rejected by G.A. Borelli in 1680 and outright ridiculed by J. Bernoulli in 1694. The anatomical correctness and predictive value was rightfully acknowledged only towards the Millennium. In Part Two, the Canis …, Steno gave a detailed anatomical description of a giant shark’s head with focus on the likeness of its teeth and the so-called tongue stones, or “glossopetrae”, dug from the ground. Steno conjectured that remnants from sharks living in the past had become fossils due to chemical processes through interaction with the surrounding sediments at the bottom of the sea, presuming that the finding areas had been sea-covered. From studies in Part Three of reproductive organs in mammals, viviparous ray-fish and shark, he concluded that the so-called female testicles in women and mammals are analogous with ovaries of oviparous animals and should therefore be named accordingly. Two years later in the Prodromus De Solido intra Solidum, Steno described the transformation over time of sedimentary landscapes in Tuscany, and how crystals grow by accretion to the surface of entities derived from limpid sea-water or freshwater in caves. These are studies of time-related transformations of solids in organic and inorganic materials. However, such processes could not be documented by visual observation, since changes go too quickly in muscles, in the case of the landscapes because the transformations took place in the past. Thus, Steno and contemporaries put forward hypotheses on such hidden processes that were only gradually corroborated when fitting into a cluster of evidence. His considerations on crystal growth may have been triggered by an interest as a physician to know how saliva, gall and kidney stones are formed. Likewise, considerations on sharks’ replacement of their teeth could extend knowledge on dentition to bring a better cure for those who complain of being toothless. He emphasized the importance of mathematical methods to describe processes in the human body and cited from Galileo, Discourse on Bodies in Water (1612), in which physics outweighs Aristotelian rules to explain the interaction of solids and solvents. Likewise, Steno’s ‘New Myology’ was a showdown against an Aristotelean physical dogma from Physics VII: everything which moves is moved by another, which excluded fibre shortening in muscles and blinded researchers on muscle contraction for generations after Steno.

Preparation of polypropylene with high melt strength by wet reaction blending of lignin

AbstractIn this paper, the melt strength of polypropylene is shown to be significantly improved by lignin‐cooperative construction of heterophase network structure and the evolution mechanism of lignin on the topology of polypropylene is investigated. Electron paramagnetic resonance (EPR) analysis shows that the free radicals generated by polypropylene irradiation can remain active for 2 weeks; rheological studies show that lignin promotes the formation of heterogeneous network structures in polypropylene, and its melt is characterized by long‐chain branching. Phase angle‐complex modulus, complex viscosity‐complex modulus, Han's, and Cole–Cole curves are used to analyze the liquid–solid transformation, and the results indicate that the enhanced interfacial action is due to the formation of the heterogeneous network structures. The mechanical properties show that the impact strength is increased by 1.8 times due to the synergistic effect of lignin and acrylamide. SEM shows the formation of a fibrous network structure around the lignin, which undergoes interfacial yielding, improving the interfacial interaction between the components.

Dual Quaternion Embeddings for Link Prediction

The applications of knowledge graph have received much attention in the field of artificial intelligence. The quality of knowledge graphs is, however, often influenced by missing facts. To predict the missing facts, various solid transformation based models have been proposed by mapping knowledge graphs into low dimensional spaces. However, most of the existing transformation based approaches ignore that there are multiple relations between two entities, which is common in the real world. In order to address this challenge, we propose a novel approach called DualQuatE that maps entities and relations into a dual quaternion space. Specifically, entities are represented by pure quaternions and relations are modeled based on the combination of rotation and translation from head to tail entities. After that we utilize interactions of different translations and rotations to distinguish various relations between head and tail entities. Experimental results exhibit that the performance of DualQuatE is competitive compared to the existing state-of-the-art models.

In Situ Recombination of Elements in Spent Lithium-Ion Batteries to Recover High-Value γ-LiAlO2 and LiAl5O8.

Recovering valuable materials from spent lithium-ion batteries is an important task because of the asymmetry in resource distribution, supply, and demand around the world. A lithium-ion battery is a combination system of various elements and their oxides. Current recovering technologies focus on the separation of valuable metal elements. They can inescapably bring secondary contamination and cost to the environment due to the addition of leachants and precipitants. To recover valuable materials, in situ recombination of elements in spent lithium-ion batteries can be a more economical and environment-friendly solution. Herein, we developed a technology based on in situ aluminothermic reduction and interstitial solid solution transformation to recover high-value γ-LiAlO2 and LiAl5O8 under vacuum and high-temperature (1723 K) conditions. It was found that the process of Li2O filling into the lattice of O-Al-O structure is an energy-reducing process, while LiAl5O8 was an existing high-energy transition-state matter. Since there was no wastewater generated, the process brought a new environment-friendly method for recovering valuable metals from spent lithium-ion batteries. This study also provides new comprehension regarding the design for high-value products' recovery from multi-element mixed wastes on an atomic scale.

Kinetic model for phase transformation of noncrystalline solids: Application to permanent densification of SiO2 glass

The phase transformation of noncrystalline solids is quite different from that of crystalline solids. To gain a better understanding, a kinetic model for pressure-induced phase transformation of noncrystalline solids is constructed by formulating activation- and free-energy distributions. The model is applied to permanent densification of $\mathrm{Si}{\mathrm{O}}_{2}$ glass, which occurs as a result of a transformation in the network structure. The model is found to be effective in reproducing interesting behavior, including the existence of an infinite number of intermediate states, each of which has a distinct compression curve like a phase, and a halt in the transformation before completion even at sufficiently high temperatures.

The Effect of Void Arrangement on the Pattern Transformation of Porous Soft Solids under Biaxial Loading

Structural topology and loading condition have important influences on the mechanical behaviors of porous soft solids. The porous solids are usually set to be under uniaxial tension or compression. Only a few studies have considered the biaxial loads, especially the combined loads of tension and compression. In this study, porous soft solids with oblique and square lattices of circular voids under biaxial loadings were studied through integrated experiments and numerical simulations. For the soft solids with oblique lattices of circular voids, we found a new pattern transformation under biaxial compression, which has alternating elliptic voids with an inclined angle. This kind of pattern transformation is rarely reported under uniaxial compression. Introducing tensile deformation in one direction can hamper this kind of pattern transformation under biaxial loading. For the soft solids with square lattices of voids, the number of voids cannot change their deformation behaviors qualitatively, but quantitatively. In general, our present results demonstrate that void morphology and biaxial loading can be harnessed to tune the pattern transformations of porous soft solids under large deformation. This discovery offers a new avenue for designing the void morphology of soft solids for controlling their deformation patterns under a specific biaxial stress-state.

Polymorphism and surface diversity arising from stress-induced transformations – the case of multicomponent forms of carbamazepine

Stress-induced transformations of labile multicomponent organic solids may have a significant impact on industrial manufacturing processes, for example, in the pharmaceutical field. This study considers 15 carbamazepine (CBZ) multicomponent crystal forms, with the aim of identifying the structural and surface features that drive the outcome of thermal stress-induced transformations. Analysis of the crystal structures, and specifically the degree of similarity with the CBZ polymorphs produced by desolvation-like processes, identifies some degree of correlation between structural features. In particular, mutually exclusive supramolecular motifs identified previously within CBZ crystal structures are frequently (but not invariably) preserved, and thereby provide some indication of the anticipated polymorphic outcome. This is broadly consistent with established models relating reactant and product crystal phases. Some of the CBZ multicomponent materials show surface modifications indicative of the formation of a liquid intermediate phase, which provides an alternative dissolution/recrystallization mechanism and different polymorphic outcomes compared to the direct solid–solid transformation pathway. Other cases show intermediates of varying stoichiometry and instances of chemical decomposition. Hence, the product of thermal decomposition is frequently affected by the physical properties of the coformer, such as boiling point and reactivity. This can lead to a dependence on experimental conditions, especially when events such as recrystallization, chemical decomposition of the coformer, solubilization and peritectic melting occur concomitantly. This study highlights that the overall picture is complex, even within this series of closely related materials.

On equilibrium two-phase microstructures at plane strain

Stress-induced phase transformations in linear elastic solids are considered for the case of plane strain on the basis of a previously developed procedure that includes finding the optimal composite microstructures which provide the exact lower bound of the energy and the equilibrium new phase volume fraction that satisfies the thermodynamic equilibrium condition. Stress–strain diagrams are constructed for various deformation paths on which phase transformations are controlled by average strains or by different components of average strain and average stresses. Strain hardening and strain softening effects are demonstrated on the path of the transformation. In the case of mixed strain-stress control, regimes for which the minimizing volume fraction does not correspond to any optimal microstructure, or optimal microstructures which could not satisfy the thermodynamic equilibrium condition with respect to the new phase volume fraction, are presented. It is shown that this leads to the incompleteness of a gradual phase transformation, jump-like transformation behavior, and jump in stress. An indifferent equilibrium regime is also discussed.

Multi-material circulation optimization of the calcification-carbonation process based on material balance and phase transformation for cleaner production of alumina

The calcification-carbonation process is a novel cleaner production method to recover alkali and alumina from bauxite residue and obtain harmless residue with low aluminum content and no alkali. At present, this method is only limited to laboratory research and has not been put into industrial application. The reason is that the existing research only focuses on the mineral transformation of the solid phase, but lacks consideration of the concentration and availability of the extract in the liquid phase. The calcification-carbonation process is a complex hydrometallurgical series process. Without a complete continuous production line, it is difficult to evaluate the reliable concentration distribution in the system. In order to obtain the concentration distribution of Na2O and Al2O3 in the whole calcification-carbonation process, this paper adopts a combined research method of metallurgical process simulation and experimental research based on the existing solid phase transformation theory. This method turns out to be effective and inexpensive to develop new technology at present. On the basis of the previous experimental results of solid structure transformation and parameter optimization, this study employs the material balance analysis module of METSIM software to analyze the distribution and concentration of Na2O and Al2O3 in the calcification-carbonation process. Combined with the concentration characteristics of input and output and the experimental verification of the key steps, a multi-material circulation optimization scheme of the calcification-carbonation process through the integration of liquid material flow resources is proposed to realize the effective recovery of low-concentration Al2O3 and the circulation of alkali liquor in the system. It promotes the recycling of resources and cleaner production of alumina.

Mesomorphic Intermediate Stages During Brill Transition of Nylon 6/6

The Brill transition in nylon 6/6 is generally perceived as a fully reversible solid–solid transformation between a low-temperature triclinic lattice (α-phase) and a high-temperature pseudohexagona...

A pandemia de SARS-CoV-2: cenários epidemiológicos e medidas de correlações

The Coronavirus pandemic has been one of the most complex public health problems, in its magnitude, up to the present moment in human history. One possibility to guide public policies to combat this disease is the proposition of predictive models regarding the dissemination of SARS-CoV-2. This article aims to present some methods, non-linear fits and computational models used to estimate Coronavirus propagation in countries such as Italy and Brazil. We highlight the proposition of a Solid State Physics Model as a forecasting method. A sigmoid curve specifically used in solid materials transformation processes: the Avrami or Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Also noteworthy are the SEIAHR model and the non-linear adjustments through Gaussians. Finally, we can infer that the methodologies used were able to propose a pattern for the process of dissemination of Coronavirus in the regions studied.

Direct synthesis of shaped MgAPO-11 molecular sieves and the catalytic performance in n-dodecane hydroisomerization.

In industrial application, molecular sieves are usually used in a certain shape. This requires the addition of binder and causes the reduction of both the molecular sieve content and catalytic performance. Herein, pseudo-boemite was mixed with deionized water at room temperature, followed by the drop-wise addition of phosphoric acid, magnesium acetate solution, hydrofluoric acid, di-n-propylamine and 1-ethyl-3-methyl imidazolium bromide with vigorous stirring. The molar ratio of Al2O3 : P2O5 : MgO : HF : DPA : [EMIm]Br : H2O in the gel was 1 : 1 : 0.03 : 0.18 : 0.4 : 1 : 45. Then the gel was dried, extruded and directly crystallized to form a shaped MgAPO-11 molecular sieve. X-ray diffraction, scanning electron microscopy, N2 adsorption, ammonia temperature programmed desorption, pyridine adsorption infrared spectroscopy and nuclear magnetic resonance spectroscopy were used to investigate the physicochemical properties of the samples. X-ray diffraction, scanning electron microscopy and N2 adsorption tests show that the shaped MgAPO-11 molecular sieve is fully crystallized and possesses hierarchical porosity. Mg is incorporated into the molecular sieve framework and the Pt catalyst supported by the obtained shaped MgAPO-11 exhibits excellent catalytic performance with n-dodecane conversion of 94% and isomer selectivity of 95% at 280 °C. Such a method for the direct synthesis of shaped molecular sieves shows potential for the green synthesis of molecular sieves in industry.

Structural relaxation in layered, non-stoichiometric Fe7S8.

In this study, we investigate the kinetics of the enantiotropic solid-solid β-transition in Fe7S8 pyrrhotite, which presents a prominent example of a metal-nonmetal compound with layered crystal structure. The low-temperature (4C) and high-temperature (1C) modifications differ in their crystallographic unit-cell dimension, vacancy distribution, and magnetic ordering in the crystal lattice. Fast differential scanning calorimetry (FDSC) reveals that cooling of the paramagnetic 1C phase below the transformation temperature Tβ = 597 K, which is also the Curie temperature, generates a metastable phase that transforms into the ferrimagnetic 4C phase with high vacancy order upon further annealing below Tβ. Upon fast cooling, the low-temperature modification shows an energetically excited phase with higher entropy that relaxes towards the equilibrated pyrrhotite polymorph. The kinetics of the superheating and the structural relaxation as obtained from FDSC experiments provide deeper insight into the stability of Fe7S8 polymorphs. This may pave a new path to decipher in detail the kinetics of solid-solid phase transformations and the long-term lifespan of defects in Earth and synthetic materials.

Effects of particle size and mineral crystallinity on formation of Zn[sbnd]Al layered double hydroxides (LDH) on aluminum (oxyhydr)oxides

The widespread usage of zinc oxide nanoparticles (ZnO NPs) inevitably leads to its release in nature and interaction with environmental minerals. To reveal ZnO NP retention by natural aluminum (Al) minerals as layered double hydroxide (LDH) in the environments, the effects of Al (oxyhydr)oxide particle size and crystallinity on ZnAl LDH formation were investigated during ZnO NP interaction with seven different Al (oxyhydr)oxides at neutral and alkaline pHs. Dissolution kinetics displayed a decrease of dissolved Zn2+ and Al(OH)4− concentrations in a dual-solid system (ZnO and Al minerals) relative to a single-solid one (ZnO or Al minerals), suggesting a potential transformation of mixture solids. Diffraction, spectroscopic, and microscopic analyses indicated that Al (oxyhydr)oxide particle size and crystallinity had obviously impacted on ZnAl LDH formation. The composition percentage of ZnAl LDH in solid products followed the order of amorphous Al hydroxides (89.90% and 86.41% Zn species as ZnAl LDH at pH 7 and 10, respectively) > 5 nm γ-Al2O3 (41.62% and 49.62%) > 35 nm γ-Al2O3 (14.77% and 19.03%) > large size Al (oxyhydr)oxides (below 13.00%), including 70 nm γ-Al2O3, corundum, boehmite, and gibbsite. ZnAl LDH formation was regulated mainly by Al (oxyhyro)oxide crystallinity and particle size via changing Al oxide dissolution at pH 10 and Zn2+ adsorption at pH 7, whereas solution pH controlled the crystallinity of the formed ZnAl LDH. A dissolution-interaction-coprecipitation pathway was proposed to elucidate the mechanism of ZnAl LDH formation. The findings highlight the importance of substrate mineral size and crystallinity for ZnAl LDH formation in environmental settings.

Multiple β Forms of Saturated Monoacid Triacylglycerol Crystals.

We have investigated the polymorphism of triacylglycerol (TAG) crystals as they affect the qualities such as shelf life, mouth feel, and texture of chocolate and other products. Saturated monoacid TAGs, like trilaurin, are considered as models for TAG crystallization; however, there is still debate about the number of their polymorphs that exist. In this study, we characterized a set of novel polymorphs, β forms of saturated monoacid TAGs, which were obtained via different pathways depending on the crystallization history, by polarized light microscopy, X-ray diffraction, and differential scanning calorimetry. Saturated monoacid TAGs were crystallized as the unstable polymorphs, the α or β’ forms first, and then they were transformed into β forms by solid–solid transformations. The β form that had transformed from β’ changed its morphology by a polymorphic transformation, while the β form made from the α form kept its spherulite morphology. The β forms obtained showed different melting points. Additional heat treatment promoted further polymorphic transformation. Four novel β forms were found for each of the saturated monoacid TAGs, trilaurin, trimyristin, tripalmitin, and tristearin. They showed similar polymorphism with the same subcell packing.

Mechanical response of tensegrity dissipative devices incorporating shape memory alloys

To optimize the seismic performance prescribed by modern structural codes, buildings and infrastructures must provide adequate safety for design level earthquake excitations, with limited levels of damage. This paper deals with the computational modelling of a bracing system with tensegrity architecture, which operates as a lightweight mechanical amplifier of longitudinal displacements in the transverse direction, efficiently limiting the interstory drifts while dissipating energy. The proposed brace is based on a D-bar tensegrity structure with a rhomboidal shape comprising Shape-Memory Alloy (SMA) tendons. The SMA tendons can develop austenitic-martensitic (solid to solid) transformations, which enable them to amplify the signals into wide super elastic hysteresis, while subjected to mechanical cycles, comprising strains up to 6÷8%, with no residual deformations. The enhanced energy dissipation of the proposed SMA-D-bar (SMAD) braces are demonstrated through computational simulations of the response of braced frame to real earthquake events. The efficiency of the intended bracing to minimize the seismic impact of the served structure lays the foundation for the development of novel seismic energy dissipation systems integrating principles of tensegrity with superelasticity.