Tetrahedral Network Research Articles

The in vivo dissolution of tricalcium silicate bone cement.

This study aimed to investigate the in vivo dissolution of tricalcium silicate (Ca3 SiO5 , C3 S) bone cement in the rabbit femoral defect. Results indicated that C3 S paste directly integrated with the bone tissue without the protection of the bone-like apatite. Calcium silicate hydrate gel (C-S-H gel) and Ca(OH)2 were the main components of C3 S paste. The dissolution model of C3 S paste was a mass loss rather than a decrease in volume. The initial dissolution of C3 S paste (0 ~ 6 weeks) was greatly attributed to the release of Ca(OH)2 , and the later dissolution (>6 weeks) was attributed to the decalcification of C-S-H gel. Although the mass of C3 S paste could decrease by more than 19 wt % after 6 weeks of implantation, the created pores (<1μm) were not large enough for the bone tissue to migrate into C3 S paste. The loss of Ca ions also resulted in the transformation of SiO4 tetrahedrons from Q1 and Q2 to Q0 , Q3 , and Q4 in C-S-H gel. Because only isolated SiO4 tetrahedrons (Q0 ) and Ca ions could be absorbed by the bone tissue, C3 S paste gradually transformed into a silica-rich gel. The fundamental reason for no decrease in volume of C3 S paste was that the SiO4 tetrahedron network still maintained the frame structure of C3 S paste during the implantation.

K4CaSi6O15—Solving a 90‐year‐old riddle

AbstractPolycrystalline K4CaSi6O15 was prepared from (a) solid‐state reactions between stoichiometric mixtures of the corresponding oxides/carbonates and (b) combustion solution synthesis using K‐ and Ca‐nitrates, tetraethyl orthosilicate (TEOS), and glycine (fuel component) as starting reagents. The compound was characterized by powder X‐ray diffraction. Differential thermal analysis indicated that K4CaSi6O15 melts congruently at about 956°C. On cooling down from the liquid state, a distinct glass‐forming tendency was observed. Single crystals suitable for further structural investigations were obtained from sinter experiments just below the melting point. Basic crystallographic data are as follows: monoclinic symmetry, space group Pc, a = 6.9299(2) Å, b = 27.3496(9) Å, c = 12.2187(4) Å, β = 93.744(3)°, V = 2310.86(13) Å3, Z = 3. The crystal structure of K4CaSi6O15 belongs to the group of interrupted framework silicates with exclusively Q3‐units. The tetrahedral network is the first inorganic representative of the so‐called eth‐type. Charge compensation in the structure is achieved by the incorporation of potassium and calcium cations, which are coordinated by five to nine oxygen ligands. Ninety years after its first mention the present contribution proves the existence of K4CaSi6O15 as a stable phase in the ternary system K2O–CaO–SiO2.

Ultrafast phase transitions in polyamorphic materials triggered by swift heavy ion impacts

We report unexpectedly fast phase transitions inside the track as pressure and temperature develop after a swift heavy ion impact. By means of molecular dynamics simulations we reveal the origin of the core-shell fine structure observed in a-${\mathrm{Si}}_{}{\mathrm{O}}_{2}$ and a-${\mathrm{Si}}_{3}{\mathrm{N}}_{4}$, as well as the dense core in a-Si. The fine structure of the track is composed of two distinct amorphous phases that result from the different pressure levels in the core and in the shell during solidification. We link this behavior to the tetrahedral network present in these materials.

Transition pathway of hydrogen bond switching in supercooled water analyzed by the Markov state model.

In this work, we examine hydrogen-bond (H-bond) switching by employing the Markov State Model (MSM). During the H-bond switching, a water hydrogen initially H-bonded with water oxygen becomes H-bonded to a different water oxygen. MSM analysis was applied to trajectories generated from molecular dynamics simulations of the TIP4P/2005 model from a room-temperature state to a supercooled state. We defined four basis states to characterize the configuration between two water molecules: H-bonded ("H"), unbound ("U"), weakly H-bonded ("w"), and alternative H-bonded ("a") states. A 16 × 16 MSM matrix was constructed, describing the transition probability between states composed of three water molecules. The mean first-passage time of the H-bond switching was estimated by calculating the total flux from the HU to UH states. It is demonstrated that the temperature dependence of the mean first-passage time is in accordance with that of the H-bond lifetime determined from the H-bond correlation function. Furthermore, the flux for the H-bond switching is decomposed into individual pathways that are characterized by different forms of H-bond configurations of trimers. The dominant pathway of the H-bond switching is found to be a direct one without passing through such intermediate states as "w" and "a," the existence of which becomes evident in supercooled water. The pathway through "w" indicates a large reorientation of the donor molecule. In contrast, the pathway through "a" utilizes the tetrahedral H-bond network, which is revealed by the further decomposition based on the H-bond number of the acceptor molecule.

Effect of MnO and CaO substitution for BaO on the viscosity and structure of CaO-SiO2-MgO-Al2O3-BaO-MnO slag

The effect of MnO and CaO substitution for BaO on the viscosity and structure of CaO-SiO2-MgO-Al2O3-BaO-MnO slag was investigated using the rotating cylinder method and the structure was analyzed by employing FT-IR and XPS. The results showed that the viscosity at various temperatures decreased gradually when MnO content increased from 0wt% to 3wt%, and increased with BaO content rising from 0wt% to 5wt%, which was consistent with the corrected optical basicity (Λcorr). The activation energy for viscous flow (Eη) showed the similar trend. FT-IR and XPS spectra analysis indicated that both [SiO4]-tetrahedral and [AlO4]-tetrahedral were influenced by MnO and BaO content. The [SiO4]-tetrahedral and [AlO4]-tetrahedral network structures were depolymerized due to an increase in the relative fraction of free oxygen (O2−) and decrease of bridging oxygen (O0) with the increasing MnO content. As a larger amount of CaO was substituted by BaO, the trough depth of [SiO4]-tetrahedral and [AlO4]-tetrahedral bands became deeper, indicating the complexity of network structure and polymerization degree of slag increased, which led to an increase in viscosity.

Quantitative assessment of the structure of Ge20Te73I7 chalcohalide glass by first-principles molecular dynamics

First-principles molecular dynamics, within the density functional theory framework, is employed to assess the structural properties of the chalcohalide glass ${\mathrm{Ge}}_{20}{\mathrm{Te}}_{73}{\mathrm{I}}_{7}$ (gGTI). The calculated total x-ray and neutron structure factors are in quantitative agreement with the experimental counterparts. Glassy gGTI features a predominantly Ge-centered tetrahedral network moderately altered by iodine atoms. Compared to glassy ${\mathrm{Ge}}_{20}{\mathrm{Te}}_{80}$, gGTI shows a substantial decrease in the number of Ge-Te bonds as the presence of I leads to a breaking of the Ge-Te connections and favors the formation of Ge-I terminations where iodine atoms are onefold. Furthermore, we remark a concomitant increase of mixed $\mathrm{Ge}{\mathrm{Te}}_{4\ensuremath{-}x}{\mathrm{I}}_{x}$ tetrahedra and $\mathrm{Ge}{\mathrm{Te}}_{3\ensuremath{-}x}{\mathrm{I}}_{x}$ trigonal pyramidal units. A minor yet not-negligible fraction of iodine atoms forms Te-I bonds. Breaking of Ge-Te connections and formation of terminal Ge(Te)-I bonds results in a reduced average coordination number associated with an increase of undercoordinated Ge at the expense of fourfold coordinated Ge atoms. The analysis of chains and rings statistics reveals the presence of both linear and cross-linked chains made of Te and five-members rings containing at least one Te-Te or one Ge-Ge homopolar bond.

Mechanistic Origin of Superionic Lithium Diffusion in Anion-Disordered Li6PS5 X Argyrodites.

The rational development of fast-ion-conducting solid electrolytes for all-solid-state lithium-ion batteries requires understanding the key structural and chemical principles that give some materials their exceptional ionic conductivities. For the lithium argyrodites Li6PS5X (X = Cl, Br, or I), the choice of the halide, X, strongly affects the ionic conductivity, giving room-temperature ionic conductivities for X = {Cl,Br} that are ×103 higher than for X = I. This variation has been attributed to differing degrees of S/X anion disorder. For X = {Cl,Br}, the S/X anions are substitutionally disordered, while for X = I, the anion substructure is fully ordered. To better understand the role of substitutional anion disorder in enabling fast lithium-ion transport, we have performed a first-principles molecular dynamics study of Li6PS5I and Li6PS5Cl with varying amounts of S/X anion-site disorder. By considering the S/X anions as a tetrahedrally close-packed substructure, we identify three partially occupied lithium sites that define a contiguous three-dimensional network of face-sharing tetrahedra. The active lithium-ion diffusion pathways within this network are found to depend on the S/X anion configuration. For anion-disordered systems, the active site–site pathways give a percolating three-dimensional diffusion network; whereas for anion-ordered systems, critical site–site pathways are inactive, giving a disconnected diffusion network with lithium motion restricted to local orbits around S positions. Analysis of the lithium substructure and dynamics in terms of the lithium coordination around each sulfur site highlights a mechanistic link between substitutional anion disorder and lithium disorder. In anion-ordered systems, the lithium ions are pseudo-ordered, with preferential 6-fold coordination of sulfur sites. Long-ranged lithium diffusion would disrupt this SLi6 pseudo-ordering, and is, therefore, disfavored. In anion-disordered systems, the pseudo-ordered 6-fold S–Li coordination is frustrated because of Li–Li Coulombic repulsion. Lithium positions become disordered, giving a range of S–Li coordination environments. Long-ranged lithium diffusion is now possible with no net change in S–Li coordination numbers. This gives rise to superionic lithium transport in the anion-disordered systems, effected by a concerted string-like diffusion mechanism.

Structure of basaltic glass at pressures up to 18 GPa

Abstract The structures of cold-compressed basaltic glass were investigated at pressures up to 18 GPa using in situ X-ray and neutron diffraction techniques to understand the physicochemical properties of deep magmas. On compression, basaltic glass changes its compression behavior: the mean O-O coordination number (CNOO) starts to rise while maintaining the mean O-O distance (rOO) above about 2–4 GPa, and then CNOO stops increasing, and rOO begins to shrink along with the increase in the mean coordination number of Al (CNAlO) above ~9 GPa. The change around 9 GPa is interpreted by the change in contraction mechanism from bending tetrahedral networks of glass to increasing oxygen packing ratio via the increase in CNAlO. The analysis of the oxygen packing fraction (ηO) under high pressure reveals that ηO exceeds the value for dense random packing, suggesting that the oxygen-packing hypothesis recently proposed cannot account for pressure-induced structural transformations of silica and silicate glasses. The rise of the CNOO at 2–4 GPa reflects the elastic softening of fourfold-coordinated silicate glass, which may be the origin of anomalies of elastic moduli in basaltic glass at ~2 GPa previously reported by Liu and Lin (2014). The widths of both the first sharp diffraction peak and the principal peak show contrastive compression behaviors between modified silicate and silica glasses. This result suggests that modified silicate glasses represent different pressure evolutions in the intermediate- and extended-range order structures from those of silica glass, likely due to the presence of modifier cations and the resultant formations of smaller rings and cavity volume.

Structure and Connectivity in an Amorphous Silicon Oxycarbide Polymer-Derived Ceramic: Results from 2D 29Si NMR Spectroscopy

The atomic structure of the Si–O–C tetrahedral network of an amorphous silicon oxycarbide polymer-derived ceramic (PDC) of the composition SiO0.94±0.11C1.13±0.08 was studied at both the short range and the intermediate range using 1D and 2D 29Si nuclear magnetic resonance (NMR) spectroscopic techniques, respectively . The 1D 29Si magic angle-spinning NMR spectrum of the PDC indicates that the Si–O–C network consists of SiO4, SiO3C, SiO2C2, and SiC4 units with relative abundances of approximately 26, 25, 20, and 29%, respectively. The 2D 29Si extended CSA amplification spectrum of this PDC shows that the chemical shift anisotropy (Δ) of the mixed-bond SiOxC4–x units is significantly higher than that of the SiO4 units. On the other hand, the unusually high Δ-value for the SiC4 units was interpreted to be indicative of its role as the connecting element between the Si–O–C network and the free-carbon nanodomains. The 2D 29Si double-quantum correlation NMR spectrum of this PDC indicates that there is extensive direct linking between SiO4 and SiO3C units in the Si–O–C network besides the connectivity between like SiOxC4–x units, while the SiO4 and SiO2C2 units are only linked via a SiO3C unit. In contrast, the SiO3C units show no restriction in linking with the other SiOxC4–x units in the network. Finally, the SiC4 units show significant clustering, which is consistent with their spatial localization at the interface between the Si–O–C network and the sp2 C nanodomains. Such a spatial distribution of the SiOxC4–x units is argued to be consistent with their mass-fractal dimensions measured in previous studies.

Iterative Cup Overlapping: An Efficient Identification Algorithm for Cage Structures of Amorphous Phase Hydrates.

Molecular dynamics studies have revealed that the nucleation pathway of clathrate hydrates involves the evolution from amorphous to crystalline hydrates. In this study, complete cages are further classified into the standard edge-saturated cages (SECs) and nonstandard edge-saturated cages (non-SECs). Centered on studying the structure and evolution of non-SECs and SECs, we propose a novel and efficient algorithm, iterative cup overlapping (ICO), to monitor hydrate nucleation and growth in molecular simulations by identifying SECs and discuss possible causes of the instability of non-SECs. Manipulation of topological information makes it possible for ICO to avoid the repeated searches for identified cages and deduce all SECs with low time costs, improving the efficiency of identification significantly. The accuracy and efficiency of ICO were verified by comparing the identification results with other well-proven algorithms. Furthermore, it was found that non-SECs have short lifetimes and eventually decompose or reorganize into more stable structures. Some evidence suggests that the instability of non-SECs is closely related to the hydrogen-bonding configuration of water-ring aggregations that they contain. The spontaneous evolution of the hydrogen-bonding network into the tetrahedral network may be the main factor that causes the conversion of QWRAs and the evolution of non-SECs.

Bulk Glassy GeTe2: A Missing Member of the Tetrahedral GeX2 Family and a Precursor for the Next Generation of Phase-Change Materials

Vitreous germanium disulfide GeS2 and diselenide GeSe2 belong to canonical chalcogenide glasses extensively studied over the past half century. Their high-temperature orthorhombic polymorphs are congruently melting compounds, and the tetrahedral crystal and glass structure is largely preserved in the melt. In contrast, the ditelluride counterpart is absent in the Ge–Te phase diagram, which shows only a single compound, monotelluride GeTe. Phase-change materials based on GeTe have become a technologically important class of solids, and their structure and properties are also widely studied. Surprisingly, very scarce information is available for alloys having GeTe2 stoichiometry. Using a fast quenching procedure in silica capillaries, high-energy X-ray diffraction, and Raman spectroscopy supported by first-principles simulations, we show that bulk glassy GeTe2 differs substantially from the lighter GeX2 members, revealing 46% of trigonal germanium, 31% of three-fold coordinated tellurium, and only 20% of edge-sharing tetrahedra or pyramids. The fraction of homopolar Ge–Ge bonds is low; however, the population of dominant Te–Te dimers and Ten oligomers, n ≤ 10, appears to be significant. The complex structural and chemical topology of g-GeTe2 is directly related to the thermodynamic metastability of germanium ditelluride, schematically represented by the following reaction: GeTe2 ⇄ GeTe + Te. Disproportionation is complete above liquidus in the temperature range of semiconductor–metal transition, and the dense metallic GeTe2 liquid, mostly consisting of five-fold coordinated Ge species, exhibits high fluidity, strong fragility (m = 99 ± 5), and presumably a fast structural transformation rate combined with low atomic mobility in the vicinity of the glass transition temperature, favorable for reliable long-term data retention in nonvolatile memories. The observed and predicted characteristic features make GeTe2 a promising precursor for the next generation of phase-change materials, especially coupled with additional metal doping, depolymerizing the tetrahedral interconnected glass network and accelerating (sub)nanosecond crystallization.

Revisiting the stable structure of the Cu4 complex in silicon

The photoluminescence (PL) spectrum of Cu-containing silicon has a sharp zero-phonon (ZP) band at 1.014 eV, whose center called CuPL has the local symmetry C 3v . Recent studies of experiment and theory revealed that the CuPL center is attributed to the Cu(s)Cu3(i) complex, which is composed of three interstitial Cu(i) atoms around a substitutional Cu(s) atom. This complex (called C-type) has the desired symmetry. However, in this study, we show that the lowest-energy structure is different. The tetrahedral structure Cu4, called T-type, has the lowest energy, with the value being 0.26 eV lower than that of C-type. Between these two types, there is an energy barrier of 0.14 eV, which allows C-type to exist in a metastable state. Details of the electronic properties of the T-type complex are reported, by comparing with C-type and other isovalent complexes. Whereas the Cu4 tetrahedron is incorporated in silicon in a manner compatible with the tetrahedral network, it also has its own molecular orbitals that exhibit metallic characteristics, in contrast to other complexes. The ZP of the PL spectrum is likely ascribed to the backflow mode of the Cu4 tetrahedron.

Atomic structure of sodium iron phosphate glasses

AbstractThe atomic structure of a series of sodium iron phosphate glasses is studied using different experimental techniques: X‐ray and neutron diffraction (ND), infrared spectroscopy, extended X‐ray absorption fine structure (EXAFS), and X‐ray absorption near‐edge structure (XANES). Detailed information about the atomic pair correlations is obtained. The high resolution of ND in real space resolves two P–O distances at 1.48 Ǻ and 1.59 Ǻ as expected. All the glasses are found to consist of a phosphate tetrahedral network with metaphosphate chains and pyrophosphate units, and every phosphate unit is found to have two or three nonbridging oxygen (NBO) links available to coordinate with Na and Fe cations. The Fe–O coordination number in these glasses is found to decrease from 5.7 to 4.8 with increasing the Fe content, whereas the Na coordination number of approximately 5 is detected for all the samples.

Microwave Dielectric Permittivity and the Relaxation of 1,3-Dioxolane and 2,2-Dimethyl-1,3-dioxolane-4-methanol Aqueous Solutions

Results are presented from measuring the microwave dielectric properties of aqueous solutions of 1,3-dioxolane and 2,2-dimethyl-1,3-dioxolane-4-methanol at seven frequencies in the range of 5–25 GHz and temperatures of 288, 298, and 308 K. The static dielectric constants are considered, along with the times and parameters of activation of the dielectric relaxation process. Differences between hydration-induced changes in water and the effects of interaction between different groups of molecules are established for the solutions of the considered compounds. The dynamics of water molecules in solution is slowed, compared to that in pure water in both cases. It is established that this slowing is due to different molecular mechanisms of interaction between the dissolved species and the tetrahedral network of the H-bonds of the initial water.

Does Confinement Modify Preferential Solvation and H-Bond Fluctuation Dynamics? A Molecular Level Investigation through Simulations of a Bulk and Confined Three-Component Mixture.

Exploring the local environment around a dissolved solute in a bulk aqueous solution of alcohol and assessing the impact of confinement on the solvation structure is an important topic yet is much less studied. Such a study is important because it can provide critical information regarding the miscibility of an amphiphilic drug after delivery at a designated nanoscopic site and the subsequent release. The present molecular dynamics simulation study reports an in-depth investigation of the composition-dependent solvation structure around a dissolved hydrophobic solute, coumarin 153 (C153), in ambient binary mixtures of methanol and water in both bulk and under confinement. The confinement is a spherical sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelle with a diameter of 55 Å. Inter- and intraspecies H-bond fluctuation dynamics have been monitored and compared with those from the corresponding bulk binary mixtures. A systematic comparison of both solvation structure and H-bond dynamics between confined and bulk binary mixtures reveals modulation of both preferential solvation and H-bond relaxation times inside a nanoscopic environment. More specifically, confinement accentuates the preferential solvation phenomenon and facilitates di-mixing of mixture components. In addition, the present study reveals that the tetrahedral H-bond network of neat liquid water becomes severely affected upon addition of methanol, which becomes further distorted under confinement. Confinement severely affects the interspecies hydrogen bonds and makes the corresponding continuous hydrogen bonds much shorter-lived. Interestingly, structural hydrogen bond relaxation timescales become longer in confined binary mixtures than those in bulk binary mixtures.

Non-equilibrium engineering of chemically grown SiO2/Si by UV nanosecond pulsed laser annealing from the viewpoint of bias temperature instability sources

The impacts of high-temperature UV nanosecond pulsed laser annealing (LA) on a chemically grown SiO2/Si system are systematically investigated as a function of the number of irradiated pulses. A progressive transition is observed for both the tetrahedral SiO4 network and the SiO2/Si interface, being assumed to play an essential role in controlling bulk SiO2 traps and interface states. The presented results open the perspective to improve bias temperature instability of low thermal budget gate stacks by UV ns pulsed LA, particularly in emerging 3D integrations.

Bridging the gap between NMR measured mean silicate chain length and nano-scale silicate polymorphism of calcium silicate hydrates

Variable stoichiometry and silicate polymorphism in calcium-silicate-hydrates (C-S-H) has impeded the revelation of point defects distribution in the silicate tetrahedral network of C-S-H, which resembles tobermorite crystal structure with some bridging tetrahedra (BT) and paired tetrahedra (PT) vacancies in dreierketten chains. Here we use a computational approach to characterize silicate polymorphism by introducing the vacancy ratio of BT to PT (α) and establishing a three-term empirical mean chain length (MCL) formula for different calcium-to‑silicon ratios (Ca/Si) ranging from 1.2 to 2.3. The formula identifies BT and PT controls at low and high α respectively and allows an inverse mapping of polymorphic range based on NMR experiments. The proposed computational framework quantitatively describes silicate polymorphs and links NMR-measured MCL to C-S-H atomistic configurations at the molecular level.

Role of local order in anomalous ion diffusion: Interrogation through tetrahedral entropy of aqueous solvation shells

Small rigid ions perturb the water structure around them significantly. At constant viscosity, alkali cations (Li+, Na+, and so on) exhibit an anomalous non-monotonic dependence of diffusivity on ion-size, in stark violation of the Stokes-Einstein expression. Although this is a well-known problem, we find that an entropic view of the problem can be developed, which provides valuable insight. The local entropy experienced by the solute ion is relevant here, which leads to the connection with local viscosity, discussed earlier by many. Due to the strong interactions with ions, the translational and rotational entropy of solvation water decreases sharply; however, an opposite effect comes from the disruption of the tetrahedral network structure of water near the charges. We compute the tetrahedral order of water molecules (qtet) around the ion and suitably defined tetrahedral entropy [S(qtet)] that is a contribution to the excess entropy of the system. Our results reveal that although the structural properties of the second shell become nearly identical to the bulk, S(qtet) of the second shell is found to play an important role in giving rise to the non-monotonic ion-size dependence. The detailed study of the static and dynamic fluctuations in qtet and the number of hydration water molecules provides interesting insights into correlation between the structure and dynamics; the smallest static fluctuation of qtet for the first hydration shell water molecules of Li+ is indicative of the iceberg picture. The study of fluctuation properties of qtet and the coordination number also reveals the role of the second hydration layer and could explain the anomalous behavior of the Rb+ ion.

Rheological behavior of molecular vs network chalcogenide supercooled liquids.

The viscoelastic behavior of supercooled glass-forming liquids along the binary join As4S3-GeS2 with As4S3 contents varying from 81.25 to 9 mol. % and correspondingly with structures varying from predominantly molecular to a three-dimensional tetrahedral network is studied by small-amplitude oscillatory shear parallel plate rheometry. The storage shear modulus G' shows a scaling behavior of G'(ω) ∼ ωn in the terminal (low-frequency) regime, where n varies between 1 and 2 and shows an increasingly anomalous departure from the expected value of 2 (Maxwell scaling) with increasing molecule content. A concomitant departure from the Maxwell scaling is also observed for the loss modulus G″ at frequencies above the G'-G″ crossover. On the other hand, the variation in the phase angle δ with the complex modulus indicates that the molecular liquid does not display a purely viscous response even at the lowest frequencies. These results, combined with an analysis of the relaxation spectra of these liquids, suggest that the anomalous behavior of molecular liquids may be linked to their rather broad relaxation spectrum and the presence of slow relaxation processes associated with molecular clusters. Additionally, these liquids are also characterized by a wide high-frequency plateau in the relaxation spectral density that can be linked to the rotational dynamics of the constituent molecules. Such fundamental differences between the rheological behavior of molecular and network liquids may explain the significantly higher fragility of the former.

Fly ash–GGBS geopolymer in boron environment: A study on rheology and microstructure by ATR FT-IR and MAS NMR

The present study focuses on the use of borax composite sodium silicate activator (B) in place of water glass (S) in the fly ash–GGBS composite (4:1) geopolymerization. The substituent is favoured as it delivers advantages such as increased setting time and workability by mitigating the agglomeration of flocks without affecting the compressive strength of the geopolymer. Microstructural changes of boroaluminosilicate were studied with the help of ATR-FT-IR and MAS NMR. Rheology studies indicated that the borax composite pastes display shear thinning behaviour with low yield stress and fit well with the Bingham model. In-situ ATR-FT-IR spectrum revealed the severing of silica bonds by soluble [BO4] and its incorporation into the silicate backbone resulted in the drop in of Si–O–T asymmetry vibration response. The NMR spectral changes of 29Si,27Al and 11B nuclei environment in geopolymeric tetrahedral network showed that the fraction of [SiO4] and [BO4] increases upon borax addition with the diminished fraction of B3 non-rings without any specific changes in Al coordination. The tetrahedral boron absorption band in the wave numbers at 1380–1310 cm−1 and1134 cm–1is observed in FT-IR and its configuration is compatible in the reaction product.