Changes In Structure Of Material Research Articles

Elucidating nano and meso-structures of lignin carbon composites: A comprehensive study of feedstock and temperature dependence

The production of carbon materials from renewable biofeedstocks is rapidly expanding with commercial applications in the areas of advanced materials, energy storage, and biochemicals. Present-day challenges exist in understanding how the distribution of monomeric units in lignin feedstocks impacts the structure and properties of carbon composites as a function of processing. This research investigates the effect of lignin feedstock and processing conditions on the structure of carbon composites. X-ray data was collected at a synchrotron source for lignin from hardwood, softwood, and grass feedstocks, processed under varying temperature and environmental conditions. The relative abundance of the principal monomeric units—guaiacyl, p-hydroxyphenyl, and syringyl—varies with feedstock and result in reproducible variations in the x-ray data. Statistical analyses for over fifty carbon materials were performed to determine the influence of feedstock, reduction temperature, and furnace humidity. The changes in the pair distribution function correspond to changes in material structure. Taken together, the analyses support the observation that graphitic structures form and grow in size with increasing reduction temperature. The characteristic size of the graphitic crystallites varies with feedstock, with kraft softwood and organosolv switchgrass leading to carbon composites with larger graphitic domains.

Grindability of plasma sprayed thermal barrier coating using super abrasive wheel

ABSTRACTThermal Barrier Coatings (TBC) are commonly used on exhaust muffle of engines and gas turbine blades to protect the component from generated heat and increase the operational temperature. Machining of ceramic coatings is comparatively more challenging than sintered ceramics. In this study, a commonly used TBC coating, namely yttria stabilised zirconia coating was subjected to surface grinding using a mono layer nickel bonded diamond wheel. The grinding forces and specific grinding energy were studied experimentally. The normal force obtained experimentally was compared with a force model and the correlation was studied. The forces obtained were significantly low as compared to sintered YSZ and a close relationship was observed with the existing model. In addition, the specific grinding energy was also found to be minimum. This indicates that most of the energy is expended in ploughing, micro-brittle fracture and rubbing. This was ascertained through scanning electron images of the ground surface and the fragmented chips. X-Ray diffraction images of the ground sample and as-sprayed sample showed an insignificant change in material structure owing to the material removal mechanism. The surface roughness of the ground specimen was reduced significantly. The fracture toughness obtained using the Evans and Charles method was used to calculate the critical load for crack initiation and a significantly low value was observed for ductile to brittle transition. SEM images of ground chips of YSZ sample showed fragmented and broken chips indicating that the primary mode of material removal is owing to micro-brittle fracture.

A hőkezelt SiAlON kerámiák tribológiai tulajdonságai

One of the simplest volume modifying process of SiAlON ceramics which can affect the mechanical properties is the post heat-treatment. This can occur in different atmospheres, in this article the effect of oxidative heat-treatment presents both in terms of material structure changes and tribological behaviour. The post heat-treatment was carried out at 800, 1000, 1200 and 1400 ° C, the wear coefficient was determined with helps of fretting test. From the presented experiments it can be stated that the wear of SiAlON samples treated at 800 ° C decreased, while in the case of the higher temperature treated specimen some material structure changes was occurred, which adversely affected their strength properties and consequently their tribological behaviour.

Особенности воздействия ионов He и Ar низких энергий на нанопористые Si/SiO-=SUB=-2-=/SUB=--материалы

In this paper molecular dynamics simulations of low-energy (50–200 eV) ion irradiation of nanoporous Si/SiO2-based materials were performed. Obtained results confirm the experimentally observed the densification of the uppermost surface layers of materials with small (less than 1.5 nm) pores due to pore collapse initiated by incident ions. Special features of the irradiation of nanoporous materials with He and Ar low-energy ions and the influence of their energy on structural changes of materials under study are discussed.

Numerical modelling of action on transparent semiconductors of short and ultrashort laser pulses with wavelength at the material absorption edge.

The numerical model was developed of local heating a semiconductor material by laser pulses with wavelength at the area of the material intrinsic absorption edge. The mechanism of heating by nano- and picosecond pulses is based on the effect of thermal shifting the edge of the semiconductor absorption, while for femtosecond pulses the edge is shifted under acting the electric field of a light wave. The material heating by nano- and picosecond pulses can be of two types: spot-like and linear-like. In the case of femtosecond pulses the spot-like heating is realized. It was found that the local heating is accompanied by the material structure change, which corresponds to the character of heating.

Present problems of vibration isolation in heavy mining machines at long-term cyclic loads

On the basis of the developed simulation model and the Boltzmann-Volterra integral relations with kernels of relaxation and aftereffect, an equation was worked out, which made it possible to take into account the rubber viscoelastic properties in full volume; in this equation, stiffness operator of elastic suspension in the machine is written by using fractional exponential function of the Yu. Rabotnov’s type; on the basis of the mathematical model, the basic parameters of the machine under the study were calculated; in particular, for the vortex mixer, the time dependences of amplitude of the mixer housing vibrations and coefficient of vibration isolation efficiency were calculated with taking into account aging of elastic link material in the machines; the calculation results were compared with the results of industrial tests of the vortex mixer operation lasting for 16 years. The theory and method for calculating vibration isolation systems with rubber elastic links for heavy mining machines were developed with taking into account material structure changes due to the effects of aging.

Impact of Morphological and Structural Changes on Performance of Solid Oxide Cells

The durable performance of solid oxide cells (SOCs) is of great importance in their large-scale utilization. However, the degradation processes, especially the degradation of electron and ion conductive phase interface impair SOCs performance. Significant sources of such interfaces degradation represent morphological and structural changes of materials. To minimize these processes, their detailed understanding is necessary. Therefore, a series of SOCs were fabricated from commercial powders to study mechanisms of these changes under different operation conditions. Each cell was examined by electrochemical as well as by spectroscopic methods. Degradation processes were observed at electron and ion conductive phases contacts and their origin discussed.

Improving the technology of part machining by surface plastic deformation

The purpose of this work is to study the technological process of strengthening hollow cylindrical parts of tractor engines using surface plastic deformation.Experimental studies in a wide range of changes in various factors have been preliminary performed on models. The data obtained were recalculated from the model to specific parts – piston fingers and bushings of the top heads of connecting rods in automotive tractor engines. The study was aimed at determining the efforts, stresses, changes in shape, the properties and structure of a parts' material. In the course of our study, the law of similarity was maintained, whereby the sample models were geometrically similar and physically identical to parts. The rational shape of machining tools was experimentally established – conical; as well as its optimum dimensions: angle of inclination, 10°30'; magnitude of the calibration belt, 6–7 mm, which provide for the magnitude of strengthening and surface quality of the machined material. We have experimentally established the effect of angle of inclination of the machining tool on the amount of a metal sticking to its working surface. The dependence of the amount of a sticking metal on its hardness and the elasticity module has been established. We have determined the impact of height of the calibration part of a machining tool on the roughness of a part's machined surface.The empirical dependence of machining allowance with a residual deformation along the outer diameter of a piston finger has been derived based on the laboratory data obtained. It has been found that the most dangerous are the tangential stresses along the outer surface of piston fingers, which were determined in the process of deformation by a strain gauge method. We have experimentally established the value of machining allowance over a single run of the working tool at vibration deformation of piston fingers, which ensures a reduction in tensile residual stresses. Our study into the static strength of piston fingers has found that the magnitude of wear depends on the following basic factors: a machining method, the material and time of operation.The research into the weight wear of piston fingers and bushings of the top heads of connecting rods has established that at vibration deformation the amount of wear is less compared to regular expansion. The magnitude of wear of the piston fingers restored by a vibration method is 1.13 times less than that in those restored by regular expansion

Role of Zn Substitution on Improvement of Electromagnetic and Microwave Absorption Characteristics of BaTi(1-x) ZnxO3 (x = 0; 1/3; ½; 2/3; 1)

In the current study, we have explored the electromagnetic and microwave absorption characteristics, especially the permeability, permittivity and reflection loss of magnetoelectric BaTi(1-x)ZnxO3 with x = 0; 1/3; ½; 2/3; 1. The composition was selected to include the effect of structural change when Ti is substituted with Zn in BaTi(1-x)ZnxO3 material system. When x = 0, the Zn free BaTiO3 posesses a tetragonal phase with lattice parameters a = b = 3.996361 Å and c = 4.030751 Å. The lattice parameters changed when x > 0 and phase transformation as well as material structure change occurred when x = 1. In addition, the effect of the geometric effect of replacing Ti ions with Zn which has a bigger ion radius will increase the absorption of electromagnetic waves.

The rapid electrochemical activation of MoTe2 for the hydrogen evolution reaction

The electrochemical generation of hydrogen is a key enabling technology for the production of sustainable fuels. Transition metal chalcogenides show considerable promise as catalysts for this reaction, but to date there are very few reports of tellurides in this context, and none of these transition metal telluride catalysts are especially active. Here, we show that the catalytic performance of metallic 1T′-MoTe2 is improved dramatically when the electrode is held at cathodic bias. As a result, the overpotential required to maintain a current density of 10 mA cm−2 decreases from 320 mV to just 178 mV. We show that this rapid and reversible activation process has its origins in adsorption of H onto Te sites on the surface of 1T′-MoTe2. This activation process highlights the importance of subtle changes in the electronic structure of an electrode material and how these can influence the subsequent electrocatalytic activity that is displayed.

Continuously pulsed electric field treatment chamber modelling and design

The perspectives of pulsed electric field (PEF) application for rheological changes in plant materials and treatment chamber design are considered in current paper. By using some mathematical tools and experiments data, viscosity of transporting plant materials confirms proposed Bingham rheological model assumption. Experimental studies have shown the presence of structure formation in material supplied to the treatment chamber channel. An effect of PEF treatment, with changes of material structure and increasing of material plastic viscosity from 0.117 to 0.159 Pa·s for samples after treatment by a field strength of E = 8 kV/cm and the number of pulses n = 300 was found. Obtained results of pulsed electric fields application in continuously material flow can be used in pulsed electric fields technologies, equipment design and help to determine cost efficiency of treatment in industrial application.

Advanced Low-K Polymer Dielectric Materials and Interfaces for Fine-Pitch Re-Distribution-Layer (RDL) to Enable 2.5D and Fan-out Packages

The rapid increase of devices with artificial intelligence (AI) and machine learning capabilities is driving the demand for growth in compute performance. With transistor scaling reaching physical limitations, the semiconductor industry is looking to system-scaling to deliver the performance improvements. Advanced packaging architectures capable of supporting these applications are 2.5D interposers, 3D IC stacking, chiplets and fan-out based packaging. All of these architectures require high-density interconnects capable of routing >200 IOs/mm/layer. This talk demonstrates advanced ultra-thin ( <10 µm), low-Dk (< 3.0) polymer dielectric material candidates capable of achieving I/O densities of 500 IOs/mm/layer. Current commercially available solutions based on silicon interposers suffer from conductor and dielectric losses because of restrictions on the dielectric material (SiO2). Polymer based dielectrics offer a compelling alternative because of the potential to reduce the capacitance of the traces and improve power efficiency alongside compatibility with low-cost panel-scalable processes. This idea is explored will be explored in this talk and we will demonstrate through modelling and characterization that low-Dk polymer dielectrics are a superior candidate to current dielectric material candidates The choice of polymer dielectric is driven by technology trends towards a)high-density fine-pitch routing b)system level thermo-mechanical reliability c)panel-scalable processing. This work examines four dielectric material candidates comprising of 3 material classes, namely photo-sensitive epoxy, non-photo-sensitive epoxy and BCB for next-generation interconnect technology. High-speed electrical simulations indicate that low-Dk materials can support data rates of >10Gbps which overcomes the limitations faced by conventional high Dk epoxy dielectrics and SiO2 alternatives. The biggest challenge in moving towards low-Dk materials is that these polymers are typically non-polar and do not adhere well which poses challenges in package integration. This work proposes a unique approach to improve polymer/metal interfacial adhesion by creating a hybrid layer with tailorable material properties using vapor-phase-infiltration (VPI). VPI exposes the polymeric material to a metal-organic reactant such as trimethyl aluminium (TMA) in a heated environment. Diffusional kinetics of the reactant are highly dependent on each step of the sequential process such as temperature, time of hold, exposure time, and co-reactants used. This process is superior compared to Atomic Layer deposition (ALD) in promoting the diffusion of organometallic precursors into the polymer subsurface because of a hold-period after exposure. VPI thereby provides a highly adaptable process to create tunable hybrid interfaces with target properties. VPI-treated polymers showed a 3X improvement in adhesion strength at the polymer/metal interface. This work dives into the kinetic factors required to achieve this adhesion improvement and characterizes the corresponding material structure changes. In summary, advanced low-Dk polymer dielectrics capable of meeting next-generation high-performance computing requirements are discussed. This work evaluates the key performance benefits from moving to low-Dk dielectric materials and tackles a critical challenge of integrating these materials as re-distribution layer (RDL) dielectrics by demonstrating 3X improvement in adhesion using VPI.

3D-Printed Low-Cost Spectroelectrochemical Cell for In Situ Raman Measurements.

Raman spectroelectrochemistry is a powerful technique for characterizing structural changes of materials during electrochemical reactions and investigating the mechanism of film deposition and adsorption processes on the surfaces of electrodes. Moreover, in situ measurements enable identification of catalytic sites and reaction intermediates, which facilitates the comprehension of reaction mechanisms. The limitations of this technique include the high-cost and the complexity of the experimental arrangement required by commercial spectroelectrochemical cells (SEC). Thus, 3D-printing technology emerges as an excellent alternative for the production of SEC, with desirable shape, low-cost, and robustness in a short period of time. In this work, an SEC and a 3D-printed working electrode were fabricated from acrylonitrile-butadiene-styrene (ABS) and conductive graphene polylactic acid (PLA) filaments, respectively. The proposed SEC and the 3D-printed electrode were printed within 3.5 h with an estimated cost of materials of less than US $2. Then, the 3D-printed SEC and the electrode were used in a study of structural changes of Prussian blue according to different voltage bias.

Compressive response of tricalcium aluminate crystal: Molecular dynamics investigations

The compressive behavior of the pristine cubic crystal form of tricalcium aluminate has been investigated in this study at the molecular level. Comparative evaluation of two different types of loading and boundary conditions – uniaxial and triaxial strain has been demonstrated in this manuscript. The simulated responses using molecular dynamics have been compared with the available experimental and DFT (Density Functional Theory) simulation results wherever applicable. The global behavior of the material has been explained through changes in the energy contributions of the bond length and angle deformations along with contributions from the non-bonded interactions. It is observed that even though energy due to bond length influences the global response of the material for both the uniaxial and triaxial compression, energy due to bond angle deformation and non-bonded contribution only influences the global response in the uniaxial case and not the triaxial case. A comprehensive study is also presented of the dynamics of different bond lengths, bond angles along with the evolution of puckered chain at different strain levels for the two different types of compressive loading to explain the changes in the lattice structure of material with application of load.

Nickel-substituted LiMnPO4/C olivine cathode material: Combustion synthesis, characterization and electrochemical performances

Abstract Transition metals substitution in cathode materials is considered as an effective approach to improve the electrochemical performances of lithium–ion batteries. In this regard, host and Ni-substituted LiMn1-xNixPO4 (x = 0.00–0.05) olivine cathode materials were successfully synthesized by a modified solution combustion method. The structural and morphological properties were examined by X–ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM) and Raman spectroscopy. According to X-ray diffraction results, all substituted materials LiMn1-xNixPO4/C adopt an identical structure to that of the LiMnPO4 olivine structure, suggesting that the nickel ion has been well incorporated into the crystal lattice, without any changes in the host material structure. When x = 0.05, the material shows an excellent specific capacity and stability during charge/discharge process. The initial specific discharge capacity can reach up to 138.6 mAh g−1 at C/20 between 2.5 and 5 V, with a coulombic efficiency of about 91.1%. The results confirm that the cyclic stability and the electrochemical performances of LiMnPO4/C were highly improved by Ni-doping.

Disintegration and Biodegradation in Soil of PBAT Mulch Films: Influence of the Stabilization Systems Based on Carbon Black/Hindered Amine Light Stabilizer and Carbon Black/Vitamin E

This work characterized the disintegration and biodegradation of aged samples of PBAT films with and without photostabilization additives. The objective is to correlate these processes with properties affected after aging, i.e. molecular weight and gel content. Three different formulations were studied: pure polymer; PBAT with carbon black and hindered amine light stabilizer (HALS) and PBAT with carbon black and phenolic stabilizer vitamin E. The samples were monitored for 12 months. As expected, the lower level of photostabilization lead to the higher disintegration and biodegradation rates. Nevertheless, mineralization test showed that during time the differences among biodegradation rates become subtler. The crystallinity degree presented changes only at an advanced stage of degradation process, showing a reduction. The evaluation of the carbonyl index, molecular weight, surface morphology and visual analysis allowed to observe that the aged samples with lower gel content and lower molecular weight showed a faster degradation rate. The changes in material structure due to the increase of aromatic units concentration is the main hypothesis to explain the material behavior during degradation in soil.

Multiphysics simulation of moisture-graphite oxidation in MHTGR

A small amount of moisture on the ppm level could present in the primary helium coolant under normal operations of High-Temperature Gas-cooled Reactors (HTGRs). One potential safety issue related to HTGRs is the chronic moisture-graphite oxidation, which could affect the integrity of the fuel blocks and reflectors in the reactor core, and the support columns in the hot plenum. However, it is infeasible to perform chronic moisture-graphite oxidation tests under the prototypic high-pressure, high-temperature conditions over a long period of time that is comparable to the full service time, i.e., 36 months for Modular High Temperature Gas-cooled Reactor (MHTGR). As an alternate, accelerated moisture-graphite oxidation tests at the atmospheric pressure and high moisture concentrations have been performed in the literature. Through these accelerated tests, global reaction rate equations have been proposed, which makes it possible to study the moisture-graphite oxidation numerically. This paper is aimed to establish a multiphysics model that can evaluate the moisture-graphite oxidation under MHTGR normal operation condition. COMSOL Multiphysics was applied to couple the modeling of the fluid flow, heat and mass transfer, chemical reaction and material structural changes. To reduce the calculation time, the prototypic three-dimensional structures were simplified into a two-dimensional simulation domain. The performance of four nuclear grades of graphite (IG-110, 2114, PCEA, and NBG-17) over a 36-month service period was then investigated under the most likely prototypic condition of MHTGR. The simulation results indicate that most oxidation occurs in the three or four bottom fuel blocks due to their higher temperatures. In general, however, only a thin layer of about 1.5 mm into the graphite will be considerably oxidized even for those three or four bottom fuel blocks.

DEVELOPMENT OF ACOUSTIC CONTROL METHOD FOR STEEL STRUCTURES CHANGES DETECTION AND EVALUATION

Detection of defects at the stage of their origination, specifically at the stage of structural changes in the metal structures material, is the current issue. The main methods for determining the structural changes in the material of metal structures are considered, their advantages and disadvantages are analyzed, a new method for determining the structural changes using modern methods of non-destructive testing, namely ultrasonic phased arrays is proposed.

Cross-country analysis of relationship between material input structures and consumption-based CO2 emissions

This study focuses on the effects of changes in material and energy input structure on the consumption-based CO2 emissions. Previous studies demonstrated the connection between domestic structural changes including the shift toward a service economy and the increase in greenhouse gas emissions embodied in consumptions of a specific country. This study is an important follow-up research that examines the environmental effects across countries and evaluates whether or not the development levels of countries can explain those environmental effects. Specifically, we employed a multiplicative structural decomposition analysis based on the World Input–Output Database during 1995–2008 and decomposed consumption-based CO2 emissions of 40 nations into the following four inducement sources: (1) inputs from material goods (including energy) to material goods, (2) inputs from material goods to services, (3) inputs from services to material goods, and (4) inputs from services to services. The results from this paper is helpful for policymakers to identify the target segment of supply chain to reduce the domestic CO2 emissions without lowering the level of the country’s production activities.

Is Cobalt Needed in Ni-Rich Positive Electrode Materials for Lithium Ion Batteries?

LiNi1-x-yCoxAlyO2 (NCA) was developed from LiNiO2 by partially substituting Ni with Co and Al, and it has been successfully commercialized and used in electric vehicles by Panasonic and Tesla, respectively. Because Co has a relatively high price of $29.98 USD/lb as of Aug. 3, 2018, while the prices of Ni and Al are only $6.00 and $0.92 USD/lb, respectively, as reported on InfoMine (http://www.infomine.com/investment/metal-prices), reducing the Co content in NCA materials has become a priority.1 , 2 For NCA materials, substitution of Al for Ni was shown to improve the thermal stability and safety.3,4 Partial replacement of Ni with Co was thought to improve structural stability by hindering the mixing between Ni2+ and Li+ 5,6, and suppressing the multiple phase transitions during charge and discharge. Partially substituting Ni with other elements such as Mn and Mg has been investigated as well.7 , 8 However, it is hard to make a head to head comparison between the different substituents because of various synthesis conditions and analysis methods chosen by different researchers. With the increasing demand for reducing Co content, it is important to go “back to basics” and systematically study the impact of different cation substitutions. In this work, cations including Al, Co, Mn, and Mg, were selected for investigations. LixNi1-nMnO2 (M=Al, Co, Mn or Mg, n=0.05 or 0.1) were synthesized and studied with differential capacity versus voltage (dQ/dV vs. V) methods. In-situ X-ray diffraction (XRD) measurements were carried out on selected samples, and the unit cell parameters and unit cell volumes were carefully measured versus x. Figure 1a shows the clipped dQ/dV vs. V of LiNiO2, in which the peaks corresponding to the phase transitions have been circled. Figures 1b – 1d show that 5% Al, 5% Mn, or 5% Mg substitutions diminish these dQ/dV vs. V peaks, suggesting an effective suppression of the multiple phase transitions observed in LiNiO2. Figure 1e shows dQ/dV vs. V of 5% Co substitution, and it shows almost identical peak features as LiNiO2 (Figure 1a), indicating the existence of multiple phase transitions. However, the dQ/dV curves for the 5% Co and LiNiO2 samples are partially off-scale in Figures 1e and 1a, respectively. Therefore, Figures 1f – 1g show the same dQ/dV vs. V with a larger y-axis scale. Figures 1f and 1j show that both LiNiO2 and LiNi0.95Co0.05O2 have similar sharp and intense dQ/dV peaks compared to the other samples. The conclusions from dQ/dV vs. V analysis were supported by in-situ XRD measurements. The studies on 5% and 10% cation doped series showed trends in the changes in material structure and specific capacities. Based on the observed trends, a preliminary theory of how the various cations impact LiNi1-xMxO2 has been developed and will be reported. References Y. K. Sun, D. J. Lee, Y. J. Lee, Z. Chen, and S. T. Myung, ACS Appl. Mater. Interfaces, 5, 11434–11440 (2013).K. Ghatak, S. Basu, T. Das, V. Sharma, H. Kumar, and D. Datta, Phys. Chem. Chem. Phys., 120, 22805-22817 (2018).T. Ohzuku, A. Ueda, and M. Kouguchi, J. Electrochem. Soc., 142, 4033–4039 (1995).M. Guilmard, A. Rougier, M. Grüne, L. Croguennec, and C. Delmas, J. Power Sources, 115, 305–314 (2003).S. T. Myung, F. Maglia, K. J. Park, C. S. Yoon, P. Lamp, S. J. Kim, and Y. K. Sun, ACS Energy Lett., 2, 196–223 (2017).C. Delmas, I. Saadoune, and A. Rougier, J. Power Sources, 44, 595–602 (1993).H. Arai, S. Okada, Y. Sakurai, and J. Yamaki, J. Electrochem. Soc. , 144 , 3117–3125 (1997).C. C. Chang, J. Y. Kim, and P. N. Kumta, J. Electrochem. Soc., 147, 1722–1729 (2000). Figure 1. Cell voltage as a function of specific capacity (V vs. Q) of LiNiO2 (A), LiNi0.95Al0.05O2 (B), LiNi0.95Mn0.05O2 (C), LiNi0.95Mg0.05O2 (D), and LiNi0.95Co0.05O2 (E); Differential capacity as a function of cell voltage (dQ/dV vs. V) of 2nd charge and discharge of LiNiO2 (a), LiNi0.95Al0.05 O2 (b), LiNi0.95Mn0.05O2 (c), LiNi0.95Mg0.05O2 (d), and LiNi0.95Co0.05O2 (e); The same dQ/dV vs. V curves with larger Y axis scale (f – j). Figure 1