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Inorganic polymer binders (IPBs) are synthesized by the activation of aluminosilicate precursors with an alkaline solution such as sodium hydroxide. This paper studies the relationship between the composition, structure, and solubility of sodium aluminosilicate hydrates (N–A–S–(H)), the primary binding phase in IPBs. It was found that changing the aqueous Si/Al ratio had little effect on N–A–S–(H) Si/Al ratio, but small changes in the aqueous Si/Na ratio led to substantial changes in N–A–S–(H) Si/Al ratio. Early N–A–S–(H) products were found to be X‐ray amorphous, but a rapid transition to the crystalline phase faujasite occurred after several weeks of aging. The transition of the solid amorphous phase to faujasite was accompanied by a rapid drop in aqueous Si(IV) and Al(III) concentrations. Solubility products were determined, temporally, for the N–A–S–(H) before and after the transition to faujasite and represent new contributions to the literature, particularly for the amorphous state. The results presented here provide fundamental insights that are needed for the development of kinetic and thermodynamic models that can establish phase balances and evolutions of IPBs across a range of precursor compositions and synthesis conditions. [ABSTRACT FROM AUTHOR]

Abstract: Amorphization, phase transformation, and dilation cracking are 3 major deformation/failure mechanisms of monocrystalline 6H‐SiC. This paper studies their critical formation conditions and mechanisms under hydrostatic pressure and uniaxial compression and tension with the aid of large‐scale molecular dynamics simulations. It was found that under hydrostatic pressure the major deformation mechanism is amorphization, that under uniaxial compression the major mechanism turns to phase transformation at low temperature and amorphization at high temperature, and that under uniaxial tension the dominating mechanism becomes dilation cracking. Increasing the temperature reduces the thresholds significantly and brings about a heterogeneous deformation mode. The study further concluded that these deformation mechanisms and their thresholds can be predicted theoretically. [ABSTRACT FROM AUTHOR]

Forming high‐temperature α‐Al2O3 phase under soft sparking is an intriguing phenomenon in plasma electrolytic oxidation (PEO) of Al alloys, which contradicts the low energy input of the process. In this study, α‐Al2O3 doped with black CuO is formed beneath an amorphous white outer layer on Al–Cu–Li alloy by PEO in a dilute silicate electrolyte under soft sparking. In comparison, reddish coatings with dominating γ‐Al2O3 are formed under the conventional plasma discharges, although blackish inner layer with α‐Al2O3 can also be exposed by heavily polishing the samples. In order to know the underlying mechanism, temperatures at the coating surface and the underlying substrate have been monitored by a thermocouple under the conventional and soft sparking PEO regimes, respectively. Interestingly, high temperatures are detected in the case of soft sparking rather than PEO with strong discharges. The formation of CuO, quartz, and cristobalite within the soft sparking coating also supports the existence of high temperature. Hence, the formation of α‐Al2O3 under soft sparking can be resolved to the conventional thermal activation mechanism, without the need of seeking other plausible explanations. Thermal condition evaluation for soft sparking PEO suggests that values of the effective thermal conductivity during PEO process for the outer layer and the barrier layer at the coating/substrate interface might be lower than ∼0.05 and ∼0.0017 W m−1 K−1, respectively. It is believed that the amorphous structure of the outer and barrier layers effectively blocks the heat dissipation, facilitating the formation of a highly wear‐resistant inner layer with α‐Al2O3, CuO, and the other high‐temperature species under soft sparking. [ABSTRACT FROM AUTHOR]

Trimethylsilyl‐substituted polysilazanes were designed and successfully synthesized. They were used to fabricate high‐purity stoichiometric Si3N4 ceramics through pyrolysis process. Trimethylsilyl groups improved the stability of polysilazanes and easily escaped during pyrolysis, which effectively reduced oxygen and carbon content in the final polymer‐derived Si3N4. The C content of Si3N4 ceramic was below 0.06 wt%, and the O content was below 1.2 wt%. The Si3N4 ceramics remained amorphous up to 1400°C, yet they were completely transformed into α‐Si3N4 at 1500°C. Synergistic effect from low oxygen and carbon content contributed to highly stable amorphous state of Si3N4 till high temperatures. This amorphous Si3N4 ceramics could be used in cutting‐edge technology where high purity is compulsory. [ABSTRACT FROM AUTHOR]

The information burst in modern society poses new challenges to information preservation technology, both in storage efficiency, capacity, and security. Multi‐dimensional optical data storage based on the femtosecond laser direct writing technique is a promising way to face these challenges. Herein, a new optical storage method based on femtosecond laser‐induced local darkening of CdSe quantum dots doped glass is reported. Photoluminescence image and spectrum indicate that highly luminescent well‐crystallized CdSe quantum dots can be amorphized by a single femtosecond laser pulse and reconstructed by thermal treatment, resulting in reversible luminescence modulation, in which the luminous efficacy of CdSe quantum dots in glass matrix was well recovered after each cycle of writing and erasing. Complicated patterns written inside the glass and multi‐layer information are also successfully inscribed and well demonstrated. Data bit could be written by just one 380 fs single pulse with pulse energy as low as 100 nJ. The present work provides a potential way for three‐dimensional optical information storage and data encryption with low power consumption, fast writing speed, large capacity, and high security. [ABSTRACT FROM AUTHOR]

Efforts to reduce the carbon footprint associated with cement and concrete production have resulted in a number of promising lower‐emission alternatives. Still, research has emphasized a small subset of potentially useful precursor materials. With the goal of expanding the precursor pool, this work presents results of parallel literature mining and rate modeling activities. As a result of literature mining, materials with appropriate SiO2, Al2O3, and CaO concentrations were assembled into a comprehensive, representative ternary diagram. 23 000+ materials were extracted from 7000 journal articles, and 7500 materials from 6000 articles with 80 ≤ SiO2 + Al2O3 + CaO ≤105 wt% automatically classified. Both supervised and semi‐supervised models were used for dissolution rate prediction of glassy materials with all models pulling from a single data set (n = 802 reported dissolution rates from 105 different glasses). Supervised modeling utilized linear and decision tree regressions to determine features most predictive of dissolution rate, resulting in log‐linear relationships between rate and pH, inverse temperature (1/K), and non‐bridging oxygen per tetrahedron (NBO/T). Semi‐supervised modeling was observed to be more robust to broader feature inclusion, providing similar predictive ability with a relatively larger set of descriptive features. Most importantly, results indicated that models trained on data from disparate scientific communities were adequately predictive (RMSE ≈ 1), particularly under pH ≥7 conditions relevant to the cement and alkali activation communities. [ABSTRACT FROM AUTHOR]

An untapped source of amorphous SiO2, industrially generated Indian biomass ash (SA)—90% amorphous, with composition of ~60% SiO2 and ~20% unburnt carbon—can be used to produce cementitious and alkali‐activated binders. This study reports dissolution of amorphous Si from SA in 0.5 mol/L and 1 mol/L aqueous NaOH, with and without added Ca(OH)2, at SA:Ca(OH)2 wt% ratios of 100:0, 87.5:12.5, and 82.5:17.5. Monitoring of elemental dissolution and subsequent/simultaneous product uptake by ICP‐OES offers an effective process for evaluating utility of industrial wastes in binder‐based systems. After 28 days in solution, up to 68% of total Si is dissolved from SA in 1 mol/L NaOH, with values as much as 38% lower in the presence of Ca(OH)2, due to the formation of tobermorite‐like C‐S‐H. FTIR, 29Si MAS‐NMR, and XRD are used to characterize solid reaction products and observe reaction progress. Product chemistries calculated from ICP‐OES results and verified by selective dissolution in EDTA/NaOH—namely, Ca/Si of 0.6‐1 and Na adsorption of 1‐2 mmol/g—are found to be consistent with those indicated by aforementioned techniques. This indicates the efficacy of ICP‐OES in estimating product chemistry via such a methodology. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous Si2BC3N nanopowders (NPs) were heated at 1000‐1700°C temperatures for 30 minutes in 1 atm N2. The changes in phases, chemical bonds, and microstructures were investigated by XRD, XPS, NMR, TEM, and first‐principles calculation. Increases in heating temperatures lead to the nucleation and growth of SiC and BN(C) grains, along with partial transformation of SiC4 units from amorphous to β/α‐SiC, and collapse of B–C–N bonds. SiC nucleates prior to BN(C) at 1 atm, while it goes in the opposite order at high pressures (≥1 GPa). High pressures also shift the initial temperatures of crystallization of amorphous Si2BC3N NPs from 1400°C (1 atm) to 1150°C (5 GPa). [ABSTRACT FROM AUTHOR]

Abstract: Pulsed laser deposition was used to prepare amorphous thin films from (GeSe2)100−x(Sb2Se3)x system (x = 0, 5, 10, 20, 30, 40, 50, and 60). From a wide variety of chalcogenide glass‐forming systems, Ge–Sb–Se one, especially in thin films form, already proved to offer a great potential for photonic devices such as chemical sensors. This system has a large glass‐forming region which gives the possibility to adjust the chemical composition of the glasses according to required physical characteristics. The chemical composition of fabricated thin films was analyzed via X‐ray photoelectron spectroscopy (XPS) and compared to energy dispersive spectroscopy (EDS) data. The results of both techniques agree well: a small deficiency in chalcogen element and an excess of antimony was found. The structure of as‐deposited thin films has been investigated by XPS. The presence of the two main structural units, [GeSe4] and [SbSe3] proposed by Raman scattering spectroscopy data analysis, was confirmed by XPS. Moreover, XPS core level spectra analysis revealed the presence of M–M bonds (M = Ge, Sb) in (Ge,Sb)–Ge–(Se)3 and (Ge,Sb)–Sb–(Se)2 entities that could correspond to Ge‐based tetrahedra and Sb‐based pyramids where one of its Se atoms at corners is substituted by Ge or Sb ones. The content of depicted M–M bonds tends to increase with introduction of antimony in the amorphous network of as‐deposited thin films from x = 0 to x = 40 and then it decreases. XPS analysis of as‐deposited thin films shows also the presence of the (Ge,Sb)–Se–(Ge,Sb) and Se–Se–(Ge,Sb) entities. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous boron‐rich SiBCN were prepared by high‐energy ball‐milling of the mixtures of Si, graphite, h‐BN, and inorganic boron, which acted as extra boron source. The solid‐state amorphization, thermal stability, and crystallization of the boron‐rich SiBCN were studied in detail. It was suggested that mechanical alloying can drive solid‐state amorphization but also can be an initiation step for the nucleation of nanocrystals. The amorphous networks of Si‐C, C‐B, C‐C, C‐N, B‐N, and C‐B‐N bonds are detected by XPS; however, solid‐state NMR further confirms the formation of a new chemical environment around B atoms, BC3. The increases in boron content improve the thermal stability of SiBCN ceramics but weaken their oxidation resistance. Nano‐SiC crystallizes first while BN(C) forms subsequently. Boron promoting SiC crystallization may result from the reduced hindering effects of B‐N‐C nanodomains that retard SiC crystallization. [ABSTRACT FROM AUTHOR]

Abstract: Electrical measurements, dc and ac, show that (AgI)x(HgS)0.5‐x/2(As2S3)0.5‐x/2 glasses, 0.0 ≤  x ≤ 0.6, exhibit drastic changes in ionic conductivity σi with silver iodide additions. The ionic transport increases by 13 orders of magnitude with increasing silver content from ~0.002 to ~23 at.%, and the activation energy decreases from 1.05 to 0.35 eV. Two distinctly different ion transport regimes above the percolation threshold concentration, xc ≈ 30 ppm, were distinguished. The critical percolation regime at low silver content (≤ 2‐5 at.% Ag) is characterized by a random distribution of silver‐related entities and obeys a power‐law composition dependence of σi. The ion transport parameters depend on the host network connectivity, represented by the average coordination number 0>, via the critical fictive temperature T0; the calculated T0 value is comparable to the glass transition temperature for the glassy (HgS)0.5(As2S3)0.5 host matrix. In contrast, in the modifier‐controlled domain, the silver‐related entities are nonrandomly distributed. The high Ag+ ionic mobility results from interconnected tetrahedral (AgI2/2S2/2)n chains in the silver iodide content range 0.2 < x ≤ 0.5, and from 2D layers (Ag3/3I3/3)n or 3D mixed tetrahedral subnetwork (AgI3/3S1/2) in the range x > 0.5. [ABSTRACT FROM AUTHOR]

The structure of soda-lime alumino-borosilicate glass was studied using molecular dynamics simulations of samples of varying compositions containing ~20 000 atoms each. Pair distribution functions ( PDFs) of cations to oxygen were used for comparison to available experimental data to evaluate consistency between simulations and experiment. Additional PDFs and coordination of the network forming cations (Al/B/Si) to network modifiers (Ca/Na) were examined, which is difficult to measure experimentally. The results are consistent with available experimental data regarding cation-oxygen bond lengths and network former to oxygen coordination numbers. Si and Al are predominantly 4-coordinated, with a small concentration of overcoordinated species similar to experimental data. B varied as 3-coordinated, BO3, and 4-coordinated, BO4, as a function of the amount of Ca2+ and Na+ present, the ratio of Al2O3 to B2O3, and the fictive temperature of the sample, similar to experimental data. The simulations provide new information regarding the locations on the network modifiers to the +3 cations, Al and B. For instance, one Al ion can have multiple Na within 4 Å, but also the Na can be within 4 Å of several +3 cations. Such results would indicate a greater complexity of local structure that goes beyond the stoichiometric one +1 modifier ion near one +3 network former or one +2 modifier near two +3 formers in tetrahedral sites. [ABSTRACT FROM AUTHOR]

A method for quantitative X-ray diffraction analysis is developed for direct determination of the glassy phase content of fly ash in a hydrating binary blend of cement and low-calcium, siliceous fly ash. The intensity contributions of the unhydrated glassy phase of fly ash and the amorphous reaction products to the intensity pattern of the total amorphous phase in the hydrating binary blend are obtained by decomposition of the total intensity signature as a sum of component pseudo Voigt ( PV) peaks. An experimental program involving binary blends with three different low calcium siliceous fly ashes and two different curing temperatures is reported. The centers of the component PV peaks of the fly ash glassy phase fitted to the overall intensity pattern are found to be invariant. The glassy phase content of hydrating binary blends determined from the XRD method were found to agree well with the values obtained from a selective dissolution method. [ABSTRACT FROM AUTHOR]

The electric conductivity of polymer-derived amorphous silicoaluminum oxycarbide was measured as a function of temperature and pressure. The material exhibits typical amorphous semiconducting behavior, following band-tail hopping process. The characteristic temperature of the BTH process increases with increasing pressure, indicating that the density of states in the band-tail is changed by applying pressure. The piezoresistive stress coefficient of the material was calculated and increased with increasing temperature, which is different from other materials. It is found that such increase is due to the change in the characteristic temperature. [ABSTRACT FROM AUTHOR]