Incomplete Transformation Research Articles

A study of the electrolyte composition influence on the structure and properties of MAO coatings formed on AMg6 alloy

The influence of electrolysis conditions at different electrolyte compositions on the phase formation and properties of coatings obtained by microarc oxidation (MAO) on an aluminum alloy AMg6 was studied. For electrolysis, three types of electrolytes were used: alkaline electrolyte ((KOH) solution in distilled water), silicate electrolyte (with different percentages of Na 2 SiO 3 component) and complex alkaline silicate electrolyte with liquid glass (1÷12 g/l Na 2 SiO 3 ) and potassium hydroxide (1÷6 g/l KOH). An analysis of the results showed that the choice of electrolyte type and conditions of the microarc oxidation process allows a wide variation in the phase-structural state, thickness and properties of the AMg6 aluminum alloy. The criterion for the expected phase-structural state of the coatings as a result of microarc oxidation is the completeness of the γ–Al 2 O 3 →α–Al 2 O 3 transformation process during coating formation. The use of an alkaline electrolyte does not allow achieving a high hardness of the coating due to the formation of the γ-Al 2 O 3 phase and the absence of thermodynamic conditions for the γ–Al 2 O 3 →α–Al 2 O 3 transition. When using a silicate electrolyte, it is possible to significantly increase the growth rate of the coating, but at the same time, the presence of a large specific Si concentration stimulates the formation of mullite and an amorphous-like phase. The use of a combined alkaline silicate electrolyte (with different percentages of KOH+Na 2 SiO 3 ) with a low content (6 g/l) of Na 2 SiO 3 in solution stimulates the formation of mullite. This is manifested to the greatest extent with the lowest content (1 g/l) of the KOH component. At a higher content (2 g/l) of the KOH component, the processes characteristic of an alkaline electrolyte become dominant. This leads to an incomplete transformation reaction and the formation of only the γ-Al 2 O 3 phase. The achievement of the thermodynamic conditions of the γ–Al 2 O 3 →α–Al 2 O 3 conversion became possible with an increase in the specific Na 2 SiO 3 content in the electrolyte solution to 12 g/l. In this case, MAO coatings were formed on the AMg6 alloy with the highest hardness of 1500 kg/mm 2 and high electric strength of 12 V/μm

Characterization of the Interfacial Zone Between a HIPed Fe-Based Alloy and a Stainless Steel Container

Norem02, an Fe-based alloy with a high carbon and chromium content, is elaborated by hot isostatic pressing (HIP). HIP is an attractive pressure-assisted sintering technique allowing for the elaboration of dense fine-grained materials from metal powder placed in a container. AISI 316L and 304L stainless steels were chosen as container materials. Two kinds of Norem02 powders of different particle-size distributions yet rather similar chemical compositions were tested. Detailed investigations of the interfacial zone between the Norem02 and stainless steel container were performed. In both HIPed samples, a microstructural transition band of approximately 500-700 µm was found within the Norem02 near the austenitic container. The presence inside Norem02 of coarse M23C6-type carbides, as well as ferrite, was highlighted. Silicon and manganese enrichment and nickel depletion were revealed in the 316L and 304L steels. χ-phase formation was confirmed at the Norem02 grain boundaries, depending on sintering temperature and on the composition of the initial powder. σ-phase was not detected, suggesting incomplete transformation of χ-phase. Finally, carbon diffusion inside the austenitic steel was noted and quantified and a diffusion coefficient was calculated. Despite the formation of carbides inside the 304L, experimental results suggest that the carbon diffused mainly in solid solution.

In situ high-energy X-ray diffraction study of thermally-activated martensitic transformation far below room temperature in CuZr-based bulk metallic glass composites

Abstract The martensitic transformation within B2 phase plays a critical role for the ductility of CuZr-based bulk metallic glass (BMG) composites, yet the underlying mechanism for the martensitic transformation process needs further investigations. Here, we found that the onset temperature of the thermally-activated martensitic transformation for CuZr-based BMG composites was reduced to 162.7 ± 2.5 K, which is far lower than those of polycrystalline samples, due to the stabilization of the austenitic phase induced by crystalline-amorphous interfaces. In situ high-energy X-ray diffraction measurements (HEXRD) further demonstrate that the thermally-activated martensitic transformation is governed by an extremely incomplete martensitic transformation from B2 to B19’ and B33 phases without the decomposition of B2 phase which generally appears in polycrystalline samples. Due to unconfined stress states during the thermally-activated martensitic transformation, B33 phase forms more early during thermal process than deformation process. The present study provides a further understanding on the martensitic transformation behaviors of shape memory type CuZr-based BMG composites.

Complete Lorentz transformation of a charge-current density

It is generally assumed in the literature that a Lorentz transformation on a neutral current loop results in a moving current loop with a nonvanishing charge distribution and an electric dipole moment. We show in this paper that this is not, in fact, correct. The derivation that leads to the charge distribution was based on an incomplete Lorentz transformation, which transforms the charge-current four-vector [Formula: see text], but not the space–time four-vector [Formula: see text]. We show that completing the Lorentz transformation by using the variable [Formula: see text] in the moving frame, rather than keeping the rest frame time variable [Formula: see text], results in there being no induced charge density and no resulting electric dipole moment.

An observation of the binder microstructure in WC-(Co+Ru) cemented carbides using transmission Kikuchi diffraction

The microstructure of WC-(Co+Ru) cemented carbides was studied using transmission Kikuchi diffraction (TKD). We report that the CoFCC grains contain Σ3-annealing twins which undergo an incomplete martensitic transformation to form CoHCP laths on cooling below TMs. The parent CoFCC and product CoHCP phases are related via the Shoji-Nishiyama orientation relationship. Four variants of the CoHCP plates exhibit a special misorientation of 70.5 ± 0.2°〈112¯0〉. A higher transformed fraction was observed in the sample possessing the lower binder content and finer WC grains. We suggest that this is due to the availability of more WC-binder interfaces, which facilitate CoHCP plate nucleation.

EFFECT OF TENSION, COMPRESSION, AND SHEAR ON THE FORMATION OF A COMPOSITE OF Ni3AI WITH REFRACTORY INERT INCLUSIONS

The study proposes a model of reaction propagation in a dedicated section of the mixture of Ni and Al with inert filler. The model assumes that in the course of heating and reaction, the melting temperature is not reached, and the reaction takes place in the solid phase, which is possible after preliminary mechanoactivation. The problem was solved numerically. The analysis of the stress-strain state effect formed under tension, compression, and shear in the regimes of the composite synthesis has demonstrated that only uniaxial compression accelerates the reaction. In two other cases, the reaction slows down. The estimation shows that the stresses in the reaction zone are appreciably lower than on the boundary of load application. The largest deformations originate in the vicinity of thermal action. It was demonstrated that the addition of inert particles can cause incomplete transformation of the reagents into reaction products.

Effect of process parameters on the microstructure evolution of laser surface quenched Ni-Al bronze

Laser surface quenching technology was used to modify the surface microstructure of as-cast Ni-Al bronze (NAB). The modified microstructure was studied by scanning electron microscopy (SEM), and the effect of laser process parameters on microstructure evolution was investigated. It was found that a fine-grained zone with fully [Formula: see text] phase microstructure formed on the surface of NAB. The depth of the fine-grained zone increased with the increase of laser power, and surface melting occurred when the power reached a threshold value. Laser scanning at a low rate caused the coarsening of grain boundary, while too high rate led to incomplete quenching. Spot overlap ratio determined the microstructure of the superimposed area, and unsuitable ratio would cause bulky [Formula: see text] precipitation at the grain boundary or incomplete transformation from [Formula: see text] phase to [Formula: see text] phase.

MORPHOLOGICAL ASSESSMENT OF GESTATION REBUILDING OF THE VASCULAR BED IN THE UNTERINE-PLACENTAL AREA IN CASE OF IRON DEFICIENCY ANEMIA OF PREGNANCY IN THE ASPECT OF CHRONIC PLACENTAL FAILURE

According to the analysis of the results of own studies, the authors found that in the uterine-placental area during pregnancy with iron deficiency anemia of II-III degrees, there are no adequate gestational changes in 60±0.1 % of the spiral arteries, and insufficiency of venous flow is shown by the decrease of the number of vessels to 4.4±0.22 per 1 mm2 of histologic section area and signs of venous stagnation, mainly in the projection of the peripheral areas of the placenta. For the first time, in order to evaluate gestational immaturity of the uterine-placental region depending on the degree of iron deficiency anemia in the aspect of uterineplacental form of lacuna insufficiency, the technique of immunohistochemical imaging of vimentin in the walls of vessels in the projection of the attachment was applied. The revealed features of immune expression of vimentin in the walls of the spiral arteries in the observations with anemia indicated the preservation of leiomyocytes with incomplete gestational transformation of the arteries. The peculiarities of the concentration of vimentin in the walls of the vessels of the microcirculatory bed reflected the disturbances of the processes of angiogenesis and vasculogenesis in the uterine-placental region with iron deficiency anemia of II - III degrees.

Misperception of motion in depth originates from an incomplete transformation of retinal signals.

Depth perception requires the use of an internal model of the eye-head geometry to infer distance from binocular retinal images and extraretinal 3D eye-head information, particularly ocular vergence. Similarly, for motion in depth perception, gaze angle is required to correctly interpret the spatial direction of motion from retinal images; however, it is unknown whether the brain can make adequate use of extraretinal version and vergence information to correctly transform binocular retinal motion into 3D spatial coordinates. Here we tested this hypothesis by asking participants to reconstruct the spatial trajectory of an isolated disparity stimulus moving in depth either peri-foveally or peripherally while participants' gaze was oriented at different vergence and version angles. We found large systematic errors in the perceived motion trajectory that reflected an intermediate reference frame between a purely retinal interpretation of binocular retinal motion (not accounting for veridical vergence and version) and the spatially correct motion. We quantify these errors with a 3D reference frame model accounting for target, eye, and head position upon motion percept encoding. This model could capture the behavior well, revealing that participants tended to underestimate their version by up to 17%, overestimate their vergence by up to 22%, and underestimate the overall change in retinal disparity by up to 64%, and that the use of extraretinal information depended on retinal eccentricity. Since such large perceptual errors are not observed in everyday viewing, we suggest that both monocular retinal cues and binocular extraretinal signals are required for accurate real-world motion in depth perception.

Novel multicomponent organic-inorganic WPI/gelatin/CaP hydrogel composites for bone tissue engineering.

The present work focuses on the development of novel multicomponent organic-inorganic hydrogel composites for bone tissue engineering. For the first time, combination of the organic components commonly used in food industry, namely whey protein isolate (WPI) and gelatin from bovine skin, as well as inorganic material commonly used as a major component of hydraulic bone cements, namely α-TCP in various concentrations (0-70 wt%) was proposed. The results showed that α-TCP underwent incomplete transformation to calcium-deficient hydroxyapatite (CDHA) during preparation process of the hydrogels. Microcomputer tomography showed inhomogeneous distribution of the calcium phosphate (CaP) phase in the resulting composites. Nevertheless, hydrogels containing 30-70 wt% α-TCP showed significantly improved mechanical properties. The values of Young's modulus and the stresses corresponding to compression of a sample by 50% increased almost linearly with increasing concentration of ceramic phase. Incomplete transformation of α-TCP to CDHA during preparation process of composites provides them high reactivity in simulated body fluid during 14-day incubation. Preliminary in vitro studies revealed that the WPI/gelatin/CaP composite hydrogels support the adhesion, spreading, and proliferation of human osteoblast-like MG-63 cells. The WPI/gelatin/CaP composite hydrogels obtained in this work showed great potential for the use in bone tissue engineering and regenerative medicine applications.

Design, synthesis, photophysical properties and intrinsic mechanism of two difluoroboron β-diketonate complexes with TPE and N-alkyl pyrrole units

It is a hot topic to furnish aggregation-caused quenching luminogens with aggregation-induced emission (AIE) active units and explore their optical properties and inherent mechanism. In this paper, two newly designed and synthesized difluoroboron β-diketonate complexes (TPE-BF2-2AP and TPE-BF2-2MP) with tetra (phenyl) ethylene (TPE) and N-alkyl pyrrole unit exhibit solvatochromism, AIE and mechanochromic properties. Although the alkyl substituents with slight difference, TPE-BF2-2AP relative to TPE-BF2-2MP show distinct increased stokes shift and red shifted fluorescence emission in organic solvents. More interestingly, single crystal analysis reveals that TPE-BF2-2MP forms head-to-head anti-parallel stacking, while TPE-BF2-2AP adopts a scarce head-to-head cross non-parallel stacking, leading to enhanced quantum efficiency from 0.24 to 0.34 before/after grinding, and blue shifted fluorescence emission compared with TPE-BF2-2MP in aggregated states and crystalline states. In addition, the two luminogens exhibit multi-state emission properties by grinding, solvent fumigation and heating due to incomplete transformation between amorphous and crystalline state.

Delayed endometrial decidualisation in polycystic ovary syndrome; the role of AR-MAGEA11

Polycystic ovary syndrome (PCOS) is a common gynaecological disorder, with a prevalence of up to 12% of women of reproductive age, and is in part characterised by elevated circulating androgens and aberrant expression of androgen receptor (AR) in the endometrium. A high percentage of PCOS patients suffer from infertility, a condition that appears to be linked to mistimed and incomplete decidualisation critically affecting events surrounding embryo implantation. The aim of this study was to examine the involvement of MAGEA11, and the genome-wide role of AR in PCOS. We determined that elevated androgen levels on PCOS cells had an impact on the delayed and incomplete decidual transformation of endometrial cells. The AR co-regulator MAGEA11, a known enhancer of AR function, was constitutively overexpressed throughout the menstrual cycle of PCOS patients, co-localised in the nucleus of PCOS stromal tissue and cells and formed a molecular complex with AR. Genome-wide AR analysis in PCOS stromal cells revealed that AR targets included genes involved in cell death and apoptosis, as well as genes commonly dysregulated in endometrial cancer. Enhanced MAGEA11 and AR-mediated transcriptional regulation may impact on a correct endometrial decidualisation response, subsequently affecting endometrial receptivity in these infertile women.Key messagesMAGEA11 and AR are overexpressed in hyperandrogenic PCOS patients.MAGEA11-AR overexpression in PCOS correlates with delayed decidualisation.AR and MAGEA11 associate in a molecular complex.AR directly regulates a unique set of genes controlling gene differentiation.

Thermo-electro-mechanical phase-field modeling of paraelectric to ferroelectric transitions

Ferroelectric materials are widely used in engineering and science applications due to their large nonlinear thermo-electro-mechanical coupling. This paper develops and studies a phase-field model to describe paraelectric to ferroelectric phase transitions and the giant electrocaloric effect, a large adiabatic temperature change with the application of an electric field. Spatially inhomogeneous temperature distributions, latent heat due to phase changes, and heat conduction are included in the model. The model is derived from fundamental balances of force, charge, micro-force, and energy. The second law of thermodynamics further constrains the constitutive behaviors derived from a phenomenological free energy function for the material. The finite element method is applied to solve the governing equations for a selected set of boundary value problems. First, the motion of a paraelectric/ferroelectric phase boundary controlled by the application and removal of heat is simulated. Then, a model electrocaloric cooling device based on a multilayer ferroelectric capacitor is simulated through a full thermodynamic refrigeration cycle. The model geometry and boundary conditions are chosen to match realistic device configurations. The device is driven through a cycle with two adiabatic and two constant electric field legs, and compared with the analytically computed ideal bulk electrocaloric cooling cycle. Several inefficiencies arise in the device, including incomplete transformation, entropy loss due to phase boundary motion, and high energy zones with large stresses and closure domains at the electrode tip.

Increased variation in numbers of presacral vertebrae in suspensory mammals.

Restricted variation in numbers of presacral vertebrae in mammals is a classic example of evolutionary stasis. Cervical number is nearly invariable in most mammals, and numbers of thoracolumbar vertebrae are also highly conserved. A recent hypothesis posits that stasis in mammalian presacral count is due to stabilizing selection against the production of incomplete homeotic transformations at the lumbo-sacral border in fast-running mammals, while slower, ambulatory mammals more readily tolerate intermediate lumbar/sacral vertebrae. We test hypotheses of variation in presacral numbers of vertebrae based on running speed, positional behaviour and vertebral contribution to locomotion. We find support for the hypothesis that selection against changes in presacral vertebral number led to stasis in mammals that rely on dorsomobility of the spine during running and leaping, but our results are independent of running speed per se. Instead, we find that mammals adapted to dorsostability of the spine, such as those that engage in suspensory behaviour, demonstrate elevated variation in numbers of presacral vertebrae compared to dorsomobile mammals. We suggest that the evolution of dorsostability and reduced reliance on flexion and extension of the spine allowed for increased variation in numbers of presacral vertebrae, leading to departures from an otherwise stable evolutionary pattern.

КВАЗИ-ЛАГРАНЖЕВОЕ ИНТЕГРИРОВАНИЕ ДВУМЕРНЫХ УРАВНЕНИЙ ПРАНДТЛЯ И БУССИНЕСКА В НЕВЯЗКОМ ПРЕДЕЛЕ

For the hydrodynamic type systems locally describing incompressible twodimensional fluid flows without dissipation we suggest quasi-Lagrangian approach for their integration. This method is based on application of incomplete Legendre transformation when the independent variables become a Lagrangian invariant (i.e. the constant quantity along the fluid particle trajectory), instead of one of the spatial coordinate, and the rest ones which are another spatial coordinate and time. Thus, this method is based on the inverse transform of one of the spatial coordinate and by this reason differs from the the complete Legendre transformation. The classical example of the complete Legendre transformation is the Hodograph transformation applying to solve the equations for one-dimensional isoentropycal gas flows. In this paper it is shown that equation for the Lagrangian invariant after applying the incomplete Legendre transformation and introducing the stream function transforms into the linear eqation can be resolved by means of the generating function introduction. This method is turned to be effective for solving the inviscid twodimensional Prandtl equation (this equation describes the boundary layer behavior) that allows one to integrate this equation completely. In the case of the constant pressure along the boundary the parallel velocity component represents the Lagrangian invariant. The obtained solution is written through the initial data and satisfies the non-penetrate boundary condition. Analysis of this solution shows the formation of the singularity for the velocity gradient on the wall. This singularity appears as the result of breaking. At the breaking point the velocity gradient tends to infinity according to the power ~(t0–t)-1 where t0 is the singular time. This solution describes the appearance of the folding type singularity. It is shown also that the Prandtl equation admits complete integration for arbitrary dependence of pressure on the longitudinal coordinate. The simplest solution is written for the case of the constant pressure gradient. For the Boussinesq system the equation for density can be resolved by this method that reduces to one equation for the generating function. This work was supported by the RAS Presidium Program «Nonlinear dynamics: fundamental problems and applications».

Impact of fish protein concentrate on apparent viscosity and physical properties of soy protein concentrate subjected to thermomechanical treatment

The aim of this research was to investigate the plasticizing and binding effect of fish protein concentrate (FPC) on soy protein concentrate (SPC) with the use of a capillary rheometer with pre-shearing capabilities. A 3-component mixture design was used to study the effect of the variables SPC, FPC and water. Mixture models with R2 in the range of 0.703–0.998 (P < 0.01) were established for apparent viscosity, extrudate hardness and expansion parameters of the plasticized materials. Extrudate microstructure as porosity, pore size distribution, cell wall thickness and distribution, were measured with the use of X-ray microtomography and models established with R2 in the range of 0.582–0.941 (P < 0.02). The mixture components affected apparent viscosity with the highest value observed for the blend with maximum SPC concentration (1381.6 Pa s) followed by maximum FPC concentration (858.6 Pa s), and lowest for the blend with maximum water concentration (398.0 Pa s). Lowest pellet hardness (136.2 N), density (904.3 kg/m3) and highest expansion (1.44) were found for the blend with maximum SPC concentration and can be attributed to incomplete thermomechanical transformation. Extrudate physical properties and expansion were explained by the extrudate microstructure. FPC added at a concentration of 65–70 g/kg gave values of hardness, extrudate density and microstructure similar to SPC added 100 g/kg of water, confirming the potential for the use of FPC as plasticizer and binder in the fish feed extrusion process.

Theoretical and Experimental Investigation of Temperature and Phase Transformation during SAW Overlaying

The article presents the modeling of temporary temperature and phase share calculations during SAW (submerged arc welding) overlaying of steel elements. The input heat of a melted electrode and the heat of direct electric arc impact have been taken into consideration in the temperature field solution. The characteristic areas (fusion, full and incomplete transformation), have been determined by solidus, A3 and A1 temperatures, respectively. The limit temperatures of the phase trandformations during cooling, based on the cooling rate in the temperature range 800–500 °C according to S355 steel time-temperature-transformation welding diagram, have been determined. The JMAK (Johnson–Mehl–Avrami–Kolmogorov) law and KM (Koistinen–Marburger) formula were used in the phase change kinetic description. Theoretical considerations were illustrated with examples of temperature and phase share computations for welding overlaid S355 steel plate. The analysis of the history of changes in temperature and structural components (phases) was carried out based on the results of numerical simulations as well as metallographic examination after SAW overlaying. The dimensions of the HAZ (heat-affected zone), obtained experimentally, and the structure types confirmed the results of the computation.

Double-Edged Effect of Humic Acid on Multiple Sorption Modes of Calcined Layered Double Hydroxides: Inhibition and Promotion.

Layered double hydroxides (LDHs) are a typical class of anionic clay minerals whose structural memory effect has been widely used in pollutant adsorption. However, the influencing mechanism of humic acid (HA) on the structural memory effect in adsorption is not clear. In this study, HA was extracted from black soil and sediments, and its effect on the structural memory effect of LDHs with different divalent metals was evaluated in adsorption. Borate complexed with HAs and HAs promoted the dissolution of magnesium-calcined LDHs (Mg-CLDH), which enhanced their adsorption rate by Mg-CLDH. However, the adsorbed HA caused a decline in the crystallinity of the regenerated Mg-LDH and an incomplete structural transformation, thereby resulting in decreased adsorption capacity. After the complexation of HAs with borate, the resulting compound was adsorbed on the surface of Zn-CLDH. The adsorption rate of borate was effectively improved in the initial stage, but at the same time slowed down the hydration and structural regeneration of Zn-CLDH. Meanwhile, the surface-adsorbed HAs also prevented borate from entering the newly formed layer inside the particles and led to a significant decrease in adsorption performance. When Ca-CLDH was used to adsorb borate, the process mainly occurred through the formation of ettringite. However, the presence of HAs enhanced the stability of the restructured LDHs and hindered the dissolution of Ca-CLDH and the reaction with B(OH)4- to form ettringite during the regeneration process, which severely inhibited the sorption of borate.

ESR Analysis of Industrial Needle-Coke Samples

Industrial needle-coke samples are studied. Their paramagnetic characteristics are determined over a broad range of magnetic fields. For some samples, no pronounced signal from the microwave resonator is observed. This indicates that the conversion of the molecular structure to coke is complete in those samples. For some samples, the ESR spectra contain two sharply resolved signals from centers associated with aliphatic and aromatic fragments. That indicates incomplete structural transformation.

Preeclampsia: the role of persistent endothelial cells in uteroplacental arteries

We explore the potential role of the endothelial lining of uteroplacental arteries in the pathogenesis of preeclampsia, a severe pregnancy disorder characterized by incomplete invasion of the uterine vasculature by extravillous trophoblast and angiogenic imbalance. In normal pregnancy, the endothelium disappears progressively from the uteroplacental arteries and is replaced by trophoblast and deposition of fibrofibrinoid structure, underpinning the so-called physiological transformation of uterine spiral arteries. We hypothesize that partial persistence of the endothelium, albeit injured, initiates a chain of events leading to the emergence of preeclampsia in 3 sequential stages. The first stage results in retention of the endothelium in uteroplacental arteries secondary to incomplete physiological transformation of the vessels. Consequently, the uteroplacental vessels are reactive to pathological cues, which drives local arteriopathy. The second stage starts with progressive reduction in uteroplacental blood flow, generating oxidative stress in the whole placenta, and heightened maternal inflammation in response to circulating trophoblastic debris. In the third stage, generalized endotheliosis causes systemic angiogenic imbalance, hypertension, and other clinical manifestation of preeclampsia.