Search

Understanding the response of Himalayan glaciers to global warming is vital because of their role as a water source for the Asian subcontinent. However, great uncertainties still exist on the climate drivers of past and present glacier changes across scales. Here, we analyse continuous hourly climate station data from a glacierized elevation (Pyramid station, Mount Everest) since 1994 together with other ground observations and climate reanalysis. We show that a decrease in maximum air temperature and precipitation occurred during the last three decades at Pyramid in response to global warming. Reanalysis data suggest a broader occurrence of this effect in the glacierized areas of the Himalaya. We hypothesize that the counterintuitive cooling is caused by enhanced sensible heat exchange and the associated increase in glacier katabatic wind, which draws cool air downward from higher elevations. The stronger katabatic winds have also lowered the elevation of local wind convergence, thereby diminishing precipitation in glacial areas and negatively affecting glacier mass balance. This local cooling may have partially preserved glaciers from melting and could help protect the periglacial environment.

Good-performing sodium solid electrolytes (SSEs) are essential for constructing all-solid-state sodium-ion batteries operating at ambient temperature. Sulfide solid electrolyte, Na3SbS4(NBS), an excellent SSE with good chemical stability in humid air, can be synthesized with low-cost processing. However, Na3SbS4-based electrolytes with liquid-phase synthesis exhibit conductivities below milli-Siemens per centimeter. Thus, a series of halogen-doped samples formulated as Na3–xSbS4–xMx(0 ≤ x≤ 0.3, M = Cl, Br, and I) were experimentally prepared in this study using the solid-state method to improve the battery performance. X-ray diffraction with refinement analysis and Raman spectroscopy were employed to understand deeply the connection between the crystal structure and conductivity of Na+ions. In addition, symmetric sodium batteries with Na2.85SbS3.85Br0.15were tested at room temperature, and pristine Na3SbS4was used as the control group. The result showed that the symmetric sodium battery assembled with the Na2.85SbS3.85Br0.15electrolyte can stably cycle for longer than 100 h at a current density of 0.1 mA/cm2. This research provides a method to manufacture novel SSEs by elaborating the effect of halogen doping in NBS.

Chalcogenide solid-state electrolytes (SEs) have been regarded as promising candidates for lithium dendrite suppression due to their high ionic conductivity, suitable mechanical strength, and large Li+ion transference number. However, the wide applications of SEs in pragmatic all-solid-state batteries are still retarded by their limited interface stability, which leads to lithium dendrite growth and formation of interphase with high resistance. In addition, the interphase evolution mechanism between SEs and metallic Li anodes remains unclear. Herein, this work demonstrates that the interfacial stability of Li2S–SiS2–P2S5SEs can be effectively enhanced by tuning the interphase through LiI incorporation. This strategy contributes to a high ionic conductivity of the SEs and electronic insulation interphase containing LiI. Thus, the 70(60Li2S–28SiS2–12P2S5)–30 LiI SEs prepared by melt-quenching exhibit a high ionic conductivity of 1.74 mS cm–1at room temperature and a larger critical current density of 1.65 mA cm–2at 65 °C. The cycling life of the symmetric Li|SEs|Li cell is up to 200 h without significant resistance growth at 0.1 mA cm–2at room temperature. This enhanced interface stability is revealed to originate from the in situ-formed LiI within the interphase, which prevents continual SEs degradation and suppresses lithium dendrite growth. This work provides a vital understanding of interphase evolution, which is valuable for designing SEs with long cycling stability.

The photonic properties of glass ceramics (GCs) are often enabled by encapsulating nanocrystals (NCs) and doped transition metal ions (TMIs). However, it is difficult to probe the optics-related effect between the host NCs’ band structure and doped TMIs’ d-d orbitals. Herein, perovskite-type KZnF_3:NiNCs in KF−ZnF_2−SiO_2 GCs were prepared and taken as a model system. The excited-state dynamics of host NCs and Ni ions’ d-d orbitals were studied by transient absorption spectroscopy. It presents a strong interaction between Ni’s d orbitals and the band edge, which could extract excitonic energy in photonic applications. These findings facilitate understanding and design of TMIs-doped GCs in real-life photonic applications.

South Asian monsoon crosses the Himalayan Mountains (HMs) and brings moisture for precipitations in the South Tibetan Plateau. A distinct dry‐belt was found in the north of the central HM region, where there are the highest and steepest mountains in the world. Through in situ and remote‐sensing observations and convection‐permitting numerical experiments, the current study demonstrates that the formation of the dry‐belt is mainly due to the depletion of water vapor when the monsoonal flow climbs the steep south slope of the HMs. The foehn phenomenon is notable over the north slope of the HMs, but the hot and dry downslope flow does not significantly reduce the amount of the precipitation; instead, it can delay the peak of the diurnal precipitation in the north side of the HMs. The central Himalaya Mountains (HMs) possess the highest and steepest mountains. Recent in situ and remote‐sensing observations show a dry‐belt in the north side of the central HMs. Although it is plausible to speculate that the dry‐belt results from the foehn wind on the leeside of the HMs, this study shows that the formation of the dry‐belt is mainly caused by the drastic depletion of water vapor along the south slope of central HMs. The foehn wind mainly delays the diurnal peak of precipitation but hardly reduces the amount of precipitation. A distinct dry‐belt was found in the north of the central Himalaya MountainsThe dry‐belt is mainly due to the depletion of water vapor over the south slope of the Himalaya MountainsThe foehn wind can postpone the diurnal cycle of the precipitation in the north side of the Himalaya Mountains

In the present paper, we studied the structural evolution of the glass matrix and formation of crystalline fluoride phases for 15KF–15ZnF2–70SiO2(glass A) and 25KF–25ZnF2–50SiO2(glass B) glasses upon thermal treatment employing transmission electron microscopy, X-ray diffraction (XRD), and solid-state NMR. The first step marks a phase separation into an SiO2rich phase and a phase enriched with Zn, K, and fluoride. As shown by XRD, depending on the nominal compositions, K2SiF6(for 15KF–15ZnF2–70SiO2) and KZnF3(for 25KF–25ZnF2–50SiO2) are found as the first crystalline phases being formed. Upon longer heat treatment, ZnF2is additionally formed in both cases. Surprisingly, a significant amount of SiF62–units is detected employing 29Si-MAS and 29Si{19F}CPMAS-NMR spectroscopy even in the base glass, which is completely amorphous according to the X-ray results. The vast majority of Si, however, is found in an exclusive SiO4environment as Q4, Q3, or Q2units. The large fraction of nonbridging oxygens per SiO4tetrahedron (ca. 0.7 for glass A and 0.65 for glass B) indicates quite large fluorine loss during glass synthesis (approx. 60–80%). Employing dipolar NMR techniques, i.e., 29Si–{19F}-REDOR (rotational echo double resonance) and 29Si{19F}CPMAS-NMR (cross polarization magic angle spinning), the presence of Si–F connectivity (in excess of the identified SiF62–units) could be ruled out. The observed differences in the 29Si–19F heteronuclear dipole couplings between the Si-Q4and Si Q3units—as determined by REDOR NMR—are compatible with the assumption of a core–shell structure with a mixed cation fluoride as the core and an SiO2-enriched shell.

Silver-ion-sconducting solid electrolytes with low activation energy are important because of their distinctive application potential in solid-state batteries operated within a broad temperature range, especially below room temperature. Achieving glassy solid electrolytes with high ionic conductivity, low activation energy, and good thermal stability is a continuous challenge for the design and synthesis of novel fast ion-conducting glasses. Here, we report markedly low activation energy and high room-temperature ionic conductivity in melt-quenched GeS2–Sb2S3–AgI chalcogenide glasses. Homogeneous 2.5GeS2–27.5Sb2S3–70AgI glass presenting high glass transition temperature of 135 °C shows high ionic conductivity of 9.18 × 10–3S/cm at 25 °C and low activation energy of 0.07 eV, which is the lowest among those of Ag-ion glassy electrolytes. Structural characterization by using Raman spectra suggests that, in the disordered network structure of GeS2–Sb2S3–AgI glasses, the formation of chain fragments composed by [SbS3–xIx]n, which is similar to the double chain of [(SbSI)∞]2in the SbSI crystal structure, provides possible diffusion pathways to facilitate low-barrier concerted migration of silver ions.

Wearable thermal sensors based on thermoelectric (TE) materials with high sensitivity and temperature resolution are extensively used in medical diagnosis, human–machine interfaces, and advanced artificial intelligence. However, their development is greatly limited by the lack of materials with both a high Seebeck coefficient and superior anticrystallization ability. Here, a new inorganic amorphous TE material, Ge15Ga10Te75, with a high Seebeck coefficient of 1109 μV/K is reported. Owing to the large difference between the glass-transition temperature and initial crystallization temperature, Ge15Ga10Te75strongly inhibits crystallization during fiber fabrication by thermally codrawing a precast rod comprising a Ge15Ga10Te75core and PP polymer cladding. The temperature difference can be effectively transduced into electrical signals to achieve TE fiber thermal sensing with an accurate temperature resolution of 0.03 K and a fast response time of 4 s. It is important to note that after the 1.5 and 5.5 K temperatures changed repeatedly, the TE properties of the fiber demonstrated high stability. Based on the Seebeck effect and superior flexibility of the fibers, they can be integrated into a mask and wearable fabric for human respiration and body temperature monitoring. The superior thermal sensing performance of the TE fibers together with their natural flexibility and scalable fabrication endow them with promising applications in health-monitoring and intelligent medical systems.

Nickel ion doped transparent bulk glass-ceramics containing K2SiF6, ZnF2, and KZnF3nanocrystals were elaborated to show the prospect that this novel group of oxyfluoride glass-ceramics is promising for transition metal ion based photonics. These new oxyfluoride glass-ceramics exhibit a new broadband luminescence of Ni2+ions in the intriguing near-IR spectral region ranging from 1200 to 2400 nm. Ni2+ions are incorporated into the precipitated K2SiF6, ZnF2, and KZnF3crystals, which provide octahedral sites for Ni2+and make it optically active. Taking into account the microstructure of phase separation observed by replica TEM, a detailed mechanism of phase-separation-assisted nanocrystallization was described for these oxyfluoride glasses. These results allow one to establish a full physical model of the nanocrystallization mechanism. For the precipitation of fluoride crystallites, not only can the nanometric size be explained but also the formation of different crystal phases can be controlled by the initial amorphous phase separation of droplet or interpenetrating structure with a sufficiently elaborated glass design.

Transparent KF-ZnF_2-SiO_2 glass-ceramics were prepared with the precipitation of KZnF_3:Ni^2+ nanocrystals. During excitation with a wavelength of 405 nm at room temperature, a broadband near-IR emission centered at 1695 nm with the FWHM of more than 350 nm was observed, which is originated from the T_2g3(F3)→A_2g3(F3) transition of octahedral Ni^2+ incorporated in the KZnF_3 crystalline phase. In comparison to oxide glass-ceramics, a redshift of the luminescence is observed, which is due to the low crystal field of these octahedral Ni^2+. The shift and extension of near-IR emission in the KZnF_3:Ni^2+ nanocrystals embedded in a glassy matrix do not only complete the broadband emission in the whole near-IR region for the Ni^2+ ions-based photonics, but also open an easy way to approach the broadband optical amplifier and tunable lasers operating in the wavelength region near 1800 nm, which was up to now achieved by codoping of several types of active ions.

Structural order beyond the next-nearest-neighbor structural units is of great interest in network glasses, especially in chalcogenide glasses, but little specific description can be reached. Here, the structure of pseudobinary (100 – x)GeS2–xSb2S3chalcogenide glasses is elucidated using differential scanning calorimetry, Raman scattering, and laser-induced phase transformation experiments over its full range (0 ≤ x≤ 100) of compositions. We observe two compositional thresholds of x= 40 and 50 in the calorimetric experiments, which are confirmed by Raman scattering and laser-induced phase transformation studies, respectively. Three structural features can be derived from these results: the structural motifs in this glass network are the [SbS3] pyramid and [GeS4] tetrahedra, respectively; at x≥ 40, the connection between [GeS4] tetrahedra vanishes; and at x≥ 50, the aggregation of four [SbS3] units happens, preparing for the laser-induced crystallization of Sb2S3crystallites. Combined with valuable indication from the topological thresholds, a specific structural model covering the arrangement of structural units in a large atomic scale is clarified, which can perfectly explain all the experimental results. This work provides a new way to get insight into the intermediate-range order of glass networks and understand their related physical properties.

Surface plasmon resonance (SPR) of noble metal nanoparticles (NPs) fostered a new area of nanophotonics, especially in the selective photon absorption and scattering. The precipitation of Ag NPs in glass would enhance the emission efficiency. Here, we studied the effects of annealing temperature (resulted in the increased Ag NPs’ concentration) or AgCl concentration on the luminescence properties of Er3+/Yb3+codoped bismuth-germanate glasses which were synthesized by a single-step melting–quenching technique. The SPR peak of Ag NPs appears around 600 nm, and the size of precipitated Ag NPs (spherical, hexagonal) ranges from 5 to 15 nm. With the precipitation of the Ag NPs, more intense green (527 nm, 548 nm) and red (661 nm) upconversion (UC) emission bands are observed up to 7.7, 10.1, and 6.5 folds in the glass containing 1 wt % AgCl annealed at 480 °C for 24 h, respectively. The Ag NPs embedded glasses showed significantly local field change that allowed for more bright UC emission by SPR.

Ge-Sb-Se chalcogenide glasses is a kind of excellent infrared optical material, which has been enviromental friendly and widely used in infrared thermal imaging systems. However, due to the opaque feature of Se-based glasses in visible spectral region, it's difficult to measure their homogeneity and internal defect as the common oxide ones. In this study, a measurement was proposed to observe the homogeneity and internal defect of these glasses based on near-IR imaging technique and an effective measurement system was also constructed. The testing result indicated the method can gives the information of homogeneity and internal defect of infrared Se-based chalcogenide glass clearly and intuitionally.

A series of silver (Ag^0) nanoclusters embedded in bismuthate glasses (Bi_2O_3-B_2O_3-TiO_2) were synthesized by the thermochemical reduction method. When B_2O_3 was substituted with TiO_2, the refractive index of the encapsulating medium increased, leading to redshifting of the surface plasmon resonance (SPR) absorption band of Ag^0, which was initially located at 612 nm. Z-scan measurements with femtosecond laser pulses at 800 nm showed that third-order optical nonlinearities (TONs) were significantly enhanced in the SPR redshifted samples, and calculation of the figure of merit manifested excellent performances of present Ag^0-bismuthate nanocomposites for TON-based all-optical switching.

IR-transparent β-GeS_2 crystallized glasses were fabricated by crystallization of the glass with a stoichiometric composition corresponding to target crystal and only β-GeS_2 crystallites were precipitated. A clear second-harmonic generation was observed in the crystallized glasses by the Maker fringe technique. The optical nonlinear susceptibility, χ^(2), of β-GeS_2 crystallized glasses was found to be ~7.3 pm/V, being comparable to that created by thermal/electric or other poling methods, which opens a new way to an optical converter operating in the mid-IR spectral region.