Amorphization Reaction Research Articles

Evaluation of chemical mechanical polishing characteristics using mixed abrasive slurry: A study on polishing behavior and material removal mechanism

Chemical mechanical polishing (CMP) is currently the most widely used method for material removal and surface planarization of glass. An environmentally friendly method of improving polishing performance by using a mixed abrasive slurry of ceria and diamond was proposed in this study. The results of polishing experiments showed that compared with single ceria abrasive, the materials removal rate (MRR) of the mixed abrasive slurry increased from 82.7 nm/min to 109.6 nm/min, while the surface roughness (Ra) decreased from 26.4 nm to 0.6 nm after polishing. An amorphous reaction layer formed during the CMP process was observed directly using transmission electron microscopy. Thermodynamic analysis was conducted to investigate the interfacial chemical reactions during the polishing process. A model was proposed to describe the mechanism of the materials removal.

Changes in amorphous structure and reaction acceleration during bulk polymerization of methacrylates

Changes in amorphous structure and reaction acceleration during bulk polymerization of methacrylates

Atomic structure of nanocrystalline and amorphous ASR products

Limited information about the atomic structure of amorphous and nanocrystalline alkali–silica reaction (ASR) products is available. Here, reactive molecular simulations were employed to construct a model of these products based on defective shlykovite. To introduce disorder into the models, various annealing temperatures (ranging from ambient to temperatures above silicate dissolution) were tested. Structures obtained from annealing at 700 K reproduced the main peaks observed experimentally in X-ray diffraction patterns of “ASR-P1” phase, a nanocrystalline or amorphous alkali–silica reaction product recently identified in synthetic and field concrete. Pair distribution functions and structure factors computed for this structure also compared well with previous data reported for “amorphous” ASR products. These results demonstrate that what was previously considered “amorphous” ASR products might be related to nanocrystalline defective shlykovite structures.

Imaging features of mandibular squamous cell carcinoma in a cat

A fourteen-year-old, neutered, male European Shorthair cat was referred with clinical signs of anorexia, weight loss and right sided mandibular swelling, which progressively increased in size. In addition, marked thickening and ulceration of the ipsilateral mandibular gingiva were both found. A computed tomography scan revealed marked amorphous periosteal reaction, extensive cortical disruption, moth-eaten to permeative osteolysis and moderate surrounding soft tissue swelling. The histopathological diagnosis was a grade 2 squamous cell carcinoma with infiltration in the bone and separation of bony trabeculae.

Titanium boride coating by high power diode laser alloying of amorphous boron with titanium and its surface property investigations

Present work deals with fabrication of superhard titanium boride coating on titanium surface with preplaced amorphous boron layer using high power diode laser alloying. Amorphous boron instantaneously converts into crystalline boron by the effect of high-power laser interaction, which rapidly drives the boron species into titanium liquid pool and form titanium boride precipitates by its convective flow. Negative Gibbs free energy (ΔG) and enthalpy (ΔH) of amorphous boron crystallization reaction introduces the concept of laser induced self-propagation synthesis. Gibbs free energy (ΔG) for the chemical reactions between Ti and B was calculated to confirm the spontaneous formation of titanium boride compound phases. The diffusion coefficient and activation energy were estimated to understand the phase formation and microstructural evolution. The structural phase, microstructure, microhardness and wear resistance of the laser borided titanium was investigated by XRD, optical and scanning electron microscopy, EDAX, Vickers microhardness analysis and linear reciprocating wear testing. The laser alloyed coating across the cross section shows formation of dendrites and whisker like microstructures. Average microhardness of 800–1600 HV0.2 was measured at different cross-sectional depths and an extreme hardness of about 3800–4700 HV0.2 was obtained in some regions of boron precipitates. The results showed a high negative value of Gibbs free energy of about −250 kJ/mol and −170 kJ/mol at ∼2000 °C respectively which confirms the spontaneity of TiB2 and TiB phase formation. The activation energy of the titanium boride is estimated to be 140 kJ/mol. The laser borided coating with the formation of TiB and TiB2 phases could be useful for surface engineering applications.

In-situ characterisation of the corrosion products formed on C-steel immersed in a soil-simulating solution

In this research C-steel corrosion products are allowed to form in a water-based solution containing 1000 ppm of SO42−, which simulates a highly corrosive soil. The electrode Fermi level was controlled with a three electrodes electrochemical set-up, scanning a potential window between the corrosion and the passivation regions. This, combined with in-situ Raman spectroscopy, allows to characterise the surface chemistry of the products formed according to the ongoing electrochemical reactions. When the potential is held in the stability region of the ionic species the surface state of the metal is characterised principally by the presence of lepidocrocite (γ-FeOOH) and green rust (GR-SO42−). The application of an anodic potential, simulating the effect of a DC anodic interference, combined with factors like moisture, presence of oxygen and sulphate ions contribute to develop a multicoloured (mix orange-like, yellow and green) mainly amorphous reaction product composed by a mix of iron oxide and oxi-hydroxide phases.

Large lattice mismatch of nanocomposite coating: In-situ establishment of MoS2 by precursor and desulfurization reaction

Constructing large lattice mismatch interfaces, especially two-dimensional materials such as MoS2, is the key to reaching the structural lubricity of heterogeneous structures. Large lattice mismatch prevents the nucleation of reinforcement of composite material, such as in situ synthesized MoS2 during the PEO process, thus affecting the mechanical performance. In this work, a precursor reaction, which can form an amorphous MoS3/TiO2 mixtures, is proposed, and the MoS2/TiO2 noncoherent interface with large mismatch is obtained through solid-state in situ desulfurization of suspended S with the action of reheat. Meanwhile, the precursor reaction is strongly dependent on the sulfur source concentration, which can form the interface with a large number of interfacial dislocations by regulating the concentration of sulfur source. Such edge pining noncoherent interface enables more dislocation and distortion near interface during scratch, which reduces the twist-angle dependence thus further improving the tribological properties. Additionally, these results render the herein presented amorphous precursor reaction strategy generally applicable for exhibiting broad application of in situ synthesis of reinforcement.

Micro-aluminum powder with bi- or tri-component alloy coating as a promising catalyst: Boosting pyrolysis and combustion of ammonium perchlorate

A novel design of micro-aluminum (μAl) powder coated with bi-/tri-component alloy layer, such as: Ni–P and Ni–P–Cu (namely, Al@Ni–P, Al@Ni–P–Cu, respectively), as combustion catalysts, were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate (AP) at a lower temperature in aluminized propellants. The microstructure of Al@Ni–P–Cu demonstrates that a three-layer Ni–P–Cu shell, with the thickness of ∼100 nm, is uniformly supported by μAl carrier (fuel unit), which has an amorphous surface with a thickness of ∼2.3 nm (catalytic unit). The peak temperature of AP with the addition of Al@Ni–P–Cu (3.5%) could significantly drop to 316.2 °C at high-temperature thermal decomposition, reduced by 124.3 °C, in comparison to that of pure AP with 440.5 °C. It illustrated that the introduction of Al@Ni–P–Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol. The laser ignition results showed that the ignition delay time of Al@Ni–P–Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni–P/AP (118 ms), decreased by 33.90%. Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions (7597.7 J/g) of Al@Ni–P–Cu, resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion. Moreover, it is believed to provide an alternative Al-based combustion catalyst for propellant designer, to promote the development the propellants toward a higher energy.

Enabling automated high-throughput Density Functional Theory studies of amorphous material surface reactions

Amorphous materials are increasingly considered for electronic and energy applications. However, modeling site-specific processes on amorphous materials is prohibitively expensive due to the large configuration space, and the large simulation cell needed to properly capture material properties. In this work, we develop a high-throughput workflow, powered by semiempirical methods in combination with Density Functional Theory, to simulate amorphous surfaces and utilize statistical sampling methods to assess surface reaction kinetics. We employ the Smooth Overlap of Atomic Positions (SOAP) to featurize surface species and apply a Bayesian Gaussian Mixture clustering model to perform a site reduction analysis. Finally, we automate the generation of input images for Improved-Tangent Nudged Elastic Band (IT-NEB) to simulate an etching reaction on the reduced sites. The resulting etching barriers are found to follow experimental etching trends for both amorphous silicon and amorphous carbon. Notably, our method reproduces etching barriers using a significantly reduced amount of sites (6 sites) out of all potential sites on the amorphous material surfaces. The successful site reduction method described in this study opens amorphous materials to high-throughput explorations of interfacial chemistry and surface properties.

Silver-decorated amorphous cobalt hydr(oxy)oxide as highly active catalyst for oxygen evolution reaction

“Soft” and “flexible” amorphous materials have gained traction recently due to their self-adjustability toward environmental changes. Unfortunately, poor conductivity and limited stability seriously hamper their commercial applications. In this work, we develop an Ag-decorated amorphous and efficient oxygen evolution reaction (OER) catalyst, requiring overpotentials of only 170 and 250 mV to yield current densities of 10 and 100 mA cm−2 in a 1.0 M KOH solution, respectively. The catalyst also exhibits outstanding stability, maintaining 93.1% of its initial performance after 27 h of continuous testing. When used as an air-electrode catalyst in a zinc-air battery, it recorded a charge–discharge cycle life of 330 h at a current density of 5 mA cm−2, with a voltage gap of 0.87 V. And the Ag decoration induced better electrical conductivity, more active specific surface, and higher Co3+ content are found to be the proper reasons for the catalyst’s outstanding OER performance and stability.

Surface patterning of ZrO2 ceramicsnum using Sn-Al Alloy at a low temperature

Surface patterning of ZrO2 ceramics was successfully achieved using the Sn-1Al low melting point alloy at a low process temperature under atmospheric conditions without the assistance of covering films or solder resists. The wetting behavior of Sn-1Al alloy on ZrO2 ceramic was significantly improved by ultrasonic excitation, and a continuous amorphous Al2O3 reaction layer of approximately 7 nm thickness was formed at the ZrO2/Sn-1Al interface with a local ultrasonication time of 20 s

Rice Husk Ash in Concrete

This study conducted an extensive literature review on rice husk ash (RHA), with a focus on its particle properties and their effects on the fresh, mechanical, and durability properties of concrete when used as a partial cement replacement. The pozzolanic property of RHA is determined by its amorphous silica content, specific surface area, and particle fineness, which can be improved by using controlled combustion and grinding for use in concrete. RHA particle microstructures are typically irregular in shape, with porous structures on the surface, non-uniform in dispersion, and discrete throughout. Because RHA has a finer particle size than cement, the RHA blended cement concrete performs well in terms of fresh properties (workability, consistency, and setting time). Due to the involvement of amorphous silica reactions, the mechanical properties (compressive, tensile, and flexural strength) of RHA-containing concrete increase with increasing RHA content up to a certain optimum level. Furthermore, the use of RHA improved the durability properties of concrete (water absorption, chloride resistance, corrosion resistance, and sulphate resistance). RHA has the potential to replace cement by up to 10% to 20% without compromising the concrete performance due to its high pozzolanic properties. The use of RHA as a partial cement replacement in concrete can thus provide additional environmental benefits, such as resource conservation and agricultural waste management, while also contributing to a circular economy in the construction industry.

Control of Large‐Scale Single‐Phase Ni Silicide Formation from Reactive Multilayers

The Ni/Si reactive multilayer (RML) is full of application potentials including reactive joining, igniters, and power sources. Here, the Ni/Si RMLs with atomic ratios of Ni and Si (2:1, 1:1, and 1:2) are studied, where the bilayer thickness and the total thickness are controlled to be 53 nm and 2 μm, respectively. After laser ignition, a rapid explosive reaction is observed where there are two self‐propagation wavefronts and their velocities reach 7.20 and 11.93 m s−1. The uniform, small grains, and single‐phase Ni silicides are obtained and controlled by tuning growth parameters. From the understanding of the Gibbs free energy diagram, the first wavefront comes from the solid‐state amorphization reaction between the Ni and a‐Si. The formation of the final Ni silicide causes the second wavefront. The entire reaction is described by a transient heat transfer model. It proposes a key parameter called heat loss rate, which explains the importance of RML thickness and the thermal diffusivity of the substrate. It allows to accurately control the reaction rate, which masters the final silicide phase. Thus, the oxidation of samples downgrades the reliability as the self‐propagation velocity of the two wavefronts dropped to 1.34 and 1.91 m s−1 in samples after 200 h of oxidation.

Variation in mineral composition by hydration and carbonation in calcium hydroxide matrix containing zeolite

Natural zeolite can modify the mechanical properties of concrete as a supplementary cementitious material based on pozzolanic activity. However, the pozzolanic reaction is difficult to explain because of the formation of amorphous reaction products and the complexity of concrete systems. In this study, the mineral, amorphpus phase compositions and pozzolanic reaction mechanism of zeolite were further investigated by performing X-ray diffraction (XRD) and magic angle spinning nuclear magnetic resonance (MAS NMR) analysis. Additionally, the pozzolanic activity of Ca(OH)2 (CH)/zeolite (CHZ, 0–50 wt% proportions of zeolite) specimens was investigated after 1, 3, 7, and 28 d of hydration. The pozzolanic products were identified as C-(A)-S-H gel and monocarboaluminate (AFmc) mineral. Zeolite, having a 5 wt% proportion of CHZ specimens, completely reacted after 3 d of hydration. The optimal zeolite proportion for forming AFmc minerals in CHZ specimens after hydration (HCHZ) was 5 wt%. As the zeolite proportion increased beyond 20 wt%, [Al(OH)4]- tended to react with [SiO(OH)3]- to form aluminosilicate gel instead of AFmc. After carbonation curing (CO2 concentration, 99%; gas pressure, 0.2 MPa; curing time, 2 h), the compressive strength of CHZ specimens (CCHZ) improved by 14–34% compared with that of pure CH specimens. An amorphous phase/calcite ratio of approximately 0.21 might produce an optimum strength resistance property in CCHZ. The heat released from the carbonation was beneficial for the polycondensation reaction of amorphous aluminosilicate to partially form Si[OSi]4 or Al[OSi]4 structures.

Electronic and Structural Modification of Mn3O4 Nanosheets for Selective and Sustained Seawater Oxidation.

The accomplishment of seawater electrolysis to produce green hydrogen energy needs an efficient and durable electrocatalyst with high selectivity and corrosion resistance. Here we report a free-standing amorphous nanostructured oxygen evolution reaction (OER) electrocatalyst with microvoids developed by embedding Gd-doped Mn3O4 nanosheets in a CuO-Cu(OH)2 nanostructure array (Gd-Mn3O4@ CuO-Cu(OH)2. The surface oxygen vacancies modulated the electronic structure of the catalyst and offered active sites with optimal chemisorption energy to OER intermediates. The hierarchical surface structure provides a large specific surface area, high electrical conductivity, ionic mobility, intrinsic activity for each active site, and efficient charge transfer, leading to an outstanding catalytic performance. The enhanced structural, chemical, and corrosion resistance ensures effectiveness as an anode in direct seawater electrolysis. Specifically, it needs an input voltage of 1.63 V to deliver a current density of 500 mA cm-2 in alkaline seawater, with the stability of more than 75 h of continuous electrolysis without hypochlorite formation. The high Faradaic efficiency demonstrates its potential for hydrogen fuel production from seawater.

Alloying reactions in nanostructured multilayers during intense deformation

Abstract Under intense deformation of metallic multilayer samples, a nanometer-scale layer thickness and grain size develops during repeated cold-rolling. Along with the evolution of the highly refined microstructure, a nanoscale interfacial alloying occurs that can result in an amorphization reaction. The deformation of multilayers exhibits driven system behavior during alloying. As the length scale of the layer thickness converges to the length scale of the mixing zone during rolling, amorphization develops in appreciable volumes. The results from selected experiments demonstrate that the relative specific interfacial area is the key microstructural metric to describe the deformation-driven alloying.

Microstructure dependent chemo-mechanical behavior of amorphous Si anodes for Li-ion batteries upon delithiation

Alloying-type anodes exhibit the solid-state amorphization during charging/discharging cycles. The mechanical and electrochemical properties of amorphous reaction phases have been widely explored recently. However, there is still lack of understanding of the underlying mircostructure-property relation in the delithiation behavior of alloying anodes. Here we perform molecular dynamics simulations to investigate the microstructure effect on the chemo-mechanical properties of amorphous Si ( a -Si) anodes upon delithiation. It is indicated that stress-free delithiation without sufficient structural relaxation leads to the gradual accumulation of structural disorder (the increase of excess energy) in amorphous Li-Si systems ( a -Li x Si). The creation of structural disorder during delithiation not only facilitates the plastic deformation of a -Li x Si at lower stress, but also thermodynamically destabilizes a -Li x Si associated with the drop of open-cell potentials. While upon constrained delithiation, the initial value of excess energy and reaction stress both contribute to the increase of structural disorder during delithiation process. Based on the stress-dependent chemical-potential model, the tensile stress increases open-cell potentials, and reduces the Li chemical potential which weakens the driving force for delithiation. As a result, the structural disorder and tensile reaction stress may cause the undesirable capacity fading of a -Si anodes, and is detrimental to the battery performance. • The delithiation behavior of amorphous Si anodes is simulated by MD simulations. • The structural disorder in amorphous Si is quantified by excess energy. • The effect of structural disorder on the chemo-mechanical properties is explored.

Interfacial Reactions between Si and SiO2 with Ceramic Additives

In this study, 10 wt.% ceramics—Al2O3, La2O3, Y2O3, MgO, and TiO2—were employed as additives for amorphous SiO2 after pressing and annealing at 1300 °C. The amorphous SiO2 changed to cristobalite SiO2. Through X-ray diffraction, scanning electron microscopy, and transmission electron microscopy with energy-dispersive spectrometry, the reaction phases of La2Si2O7, Y2Si2O7, and MgSiO3 (Mg2SiO4) were found in the SiO2 with 10 wt.% La2O3, Y2O3, and MgO additives. Cracks formed in the Si and SiO2–ceramic additive sites because of the difference in the coefficients of thermal expansion among the Si, SiO2, ceramic additives, and reaction phases. After Si came into contact with the SiO2–ceramics, two types of microstructures were found: those with and those without an amorphous SiO2 reaction layer at the interface. Amorphous SiO2 layer formation is due to the replacement of the Si position in SiO2 by Al3+ and Ti4+ impurities, which can break the bonds between Si atoms. The O content in the Si decreased from 6–9 × 1017 atoms/cm3 for SiO2 to less than ~1016 for SiO2–Al2O3 and SiO2–MgO. The average resistivity of the Si was 3 Ω·cm for SiO2 and decreased to 0.12–0.36 Ω·cm for the SiO2 with ceramic additives.

Effect of Si-based reductive modifying auxiliary on the recovery of iron and the cementitious reactivity of modified EAF slag

Si sludge was used as reductive modifying auxiliary during the iron component in the electric arc furnace (EAF) slag was reduced by carbon. The reduction behavior of the iron component in the EAF slag and the relationship between the mineral structure and the cementitious reactivity of the secondary slag were explored. The results show that the Si sludge can effectively reduce the iron-containing compounds in the slag. When the amount of Si sludge added is greater than 10 wt.%, the iron recovery rate exceeded 92% when reduced at 1773 K for 30 min. Si sludge has a modifying effect on EAF slag. When the amount of Si sludge is low (<10 wt.%), the content of cementitious components in the modified EAF slag is reduced, and low-activity merwinite crystals are precipitated in the slag, which reduces the cementitious reactivity. When Si sludge addition is greater than 10 wt.%, the amorphous phase content and reaction activity in the modified slag increased. The 28d compressive strength of the secondary slag with sludge addition of 14 wt.% reached 45.7 MPa.

Formation of carbon nanotubes and microsilica when obtaining crystalline silicon in three-phase electric ore smelting furnaces

The volume of silicon waste generated annually in the Irkutsk Region is 20 thousand tons per year, and the volume of waste accumulated in three sludge fields of JSC «Silicon» exceeds 3 million m3. The main type of crystalline silicon production waste is dust from gas cleaning systems of electric ore smelting furnaces. In this regard, this paper studies its chemical composition and the possibilities of using valuable components (amorphous silica, carbon nanotubes (CNT)) included in its composition. The study demonstrates that it is possible to separate this product by flotation into 3 components — sand fraction, flotation tailings enriched in SiO2, and froth enriched in carbon in the form of CNT. The structure of carbon nanotubes was studied and their physical and mechanical properties were determined: elastic modulus (2000 GPa), tensile strength (75 GPa), and thermal conductivity (4000 W/(m·K)). The amount of heat required to obtain 1 kg of CNT in electric ore smelting furnaces was calculated. Based on the material balance of commercial silicon electric smelting, it was found that 153 kg of CNT and 336 kg of flotation tailings are formed per ton of crystalline silicon during the endothermic process. Flotation tailings consist of 75 % amorphous microsilica particles. According to heat effect and Gibbs energy calculations made for amorphous microsilica formation reactions, it was found that all processes are exothermic, and the process of solid silicon carbide particles (2SiC + 3O2 → 2SiO2 + 2CO) oxidation with air oxygen has the highest thermodynamic probability. The economic efficiency of using amorphous silica to produce casting silumins was calculated, and its results clearly demonstrate a quick payback period (6 months), as well as a high level of its profitability (USD 819672).