Crystal Research and Technology最新文献

Herein a new class of optoelectronic devices beneficial for infrared light absorption and high-frequency application in the terahertz frequency domain are designed and fabricated. The devices are formed by coating a highly transparent thin layer of Nb₂O₅ onto a selenium-thin film to form Se/Nb₂O₅ (SNO) optical interfaces. Although coating of Nb₂O₅ nanosheets decreased the crystallite sizes and increased the strain and defect concentration in the hexagonal structured Se films, they successfully increased the light absorption by ≈148% in the infrared range of light. A blueshift in the energy band gap of Se from 2.02 to 2.30 eV is observed. The coating of the Nb₂O₅ onto Se suppressed the free carrier absorption in Se and Nb₂O₅. As dielectric active layers, SNO interfaces showed a major resonance dielectric peak centered at 1.67 eV. The optical conductivity and terahertz cutoff frequency analyses which are handled using the Drude-Lorentz approach revealed the highest drift mobility and free carrier concentration of 17.17 cm² Vs⁻¹ and 5.0 $��\times ��{10}^{17}�$ cm⁻³ when an oscillator of energy of 1.75 eV is activated. In addition, the terahertz cutoff frequency spectra which varied in the range of 4.0–131 THz showed the suitability of the SNO devices for terahertz technology and other optoelectronics.

TiAl based alloys are currently deployed in extreme service environments, such as jet engine turbine blades. The microstructure of these alloys is a two-phase lamellar structure, comprising of the majority γ-TiAl and the minority α₂-Ti₃Al phases. Understanding the microstructural evolution at high stresses and elevated temperatures is a key requirement to develop the next generation of these alloys. In situ hot stage TEM studies are reported of the mechanisms of lamellar instability and changes in phase fraction of both cold worked and undeformed Ti-48Al alloys. The effect of cold working on the kinetics of this instability has also been determined. Cross-sectional TEM samples are prepared on custom designed MEMS chips and in situ heating studies carried out. These results show that neck formation, break-up of lamellae, and spheroidization are the dominant mechanisms of microstructural instability. An increase in γ-TiAl phase content is also observed. The strain energy present in the α₂ and γ lamellae in cold worked samples results in microstructural instabilities occurring at lower temperatures in cold worked samples. These findings can be used to design new alloys with improved high temperature stability.

Naphtho[1,2-c:5,6-c]bis[1,2,5]chalcogendiazole is an important building block for organic devices due to its highly electron-accepting properties. However, despite being an effective unit of low band gap organic semiconductors, fewer studies have been conducted on analyzing such units to understand their crystal structure. Here the crystal structure analysis of naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole, naphtho[1,2-c:5,6-c]bis[1,2,5]oxadiazole is reported, and these brominated motifs. Crystal structures of naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazoles and its brominated compound show that the molecules form coplanar structures through N···S contacts, resulting in parallel face-to-face packing and π-π stacking. Double N···S contacts are found as a priority in such compounds. On the other hand, naphtho[1,2-c:5,6-c]bis[1,2,5]oxadiazoles gave N···H─C networks with π-π stacking. These differences will probably induce the difference in the crystal structure of the naphtho[1,2-c:5,6-c]bis[1,2,5]chalcogendiazole-based extended π-systems. Brominated one exhibits polymorphs, which works N···Br contacts or Br···Br contacts based on the interaction of the σ-hole of bromide. These investigations can be applied to the order-made synthesis of self-assembled soft matter and functional molecular crystals.

Water-mediated proton conductivity in nanoporous materials is influenced by channel water ordering and the hydrophobicity/hydrophilicity of interior walls, making metal-organic nanotubes (MONTs) useful systems for exploring these relationships due to their high crystallinity and tunable hydrophobicity. In the current study, electrochemical impedance spectroscopy is utilized to explore the proton conductivity on two metal organic nanotubes (UMONT and Cu-LaMONT) with weak hydrophobic behavior that possess extended water networks within the 1-D channels. Measurements performed at 95% RH and 20 °C indicate values of 1.63 × 10⁻⁴ S cm⁻¹ for UMONT and 3.80 × 10⁻⁴ S cm⁻¹ for Cu-LaMONT, which is lower than values for walls with acidic, hydrophilic functional groups or nanotubular materials with strictly hydrophobic behavior. Proton conductivity decreases sharply with lower humidity, with Cu-LaMONT being more sensitive to humidity changes. At low temperatures, UMONT outperforms LaMONT due to its well-established hydrogen bonding network and hydrophobic interior. The anisotropic nature of proton conduction is also confirmed through pelletized powder sample analysis, emphasizing that the conductivity occurs through the water networks located within the 1-D MONT channels. These findings emphasize the importance of understanding water–pore interactions and the resulting proton conductivity mechanisms to understand complex systems and design advanced materials.

The impact of ultrasound on the nucleation control and separation of maltol polymorphs in aqueous solution has been studied for the first time. The study involved varying ultrasound parameters such as power (ranging from 75 to 225 W), pulse rate (from 10% to 50%), and insonation time (2, 4, and 6 min) at room temperature and at different supersaturation levels. In addition to the expected effects of supersaturation on induction time, nucleation, and morphology of the maltol polymorphs, ultrasound is found to have a significant influence on nucleation control and separation of the polymorphs. The results reveal that ultrasound promotes the nucleation of maltol polymorphs with shorter induction times by creating nucleation hot spots through cavitation effect, and improves the quality of the crystals. Notably, under specific conditions, ultrasound induces the nucleation of a rare metastable Form-II polymorph of maltol in aqueous solution, while without ultrasound, only the stable Form-I polymorph is obtained. Morphology of the nucleated polymorphs is observed using in situ optical microscopy, and their structure is confirmed through powder X-ray diffraction (PXRD) and single crystal X-ray diffraction (SCXRD) analyses. Furthermore, thermal stability of the grown stable Form-I and metastable Form-II polymorphs of maltol is verified using differential scanning calorimetry (DSC).

The effect of rotational speeds on the growth kinetics of KDP crystal (101) faces is explored by the Michelson interference technique. The experimental results show that the growth rates rise as the rotational speed increases. The decrease in rotational speed affects the slopes of growth hillock on KDP crystal (101) faces, resulting in an overall decrease in the slopes. The kinetic coefficient of KDP crystal (101) face increases with increasing rotational speeds, and always βI, βII>βIII.

Ammonium perchlorate (AP) is a widely used solid oxidizer in solid propellant formulations, with its particle size and crystal habit significantly affecting performance. Since controlling these properties remains challenging, this study employs an intensified crystallization strategy, specifically a cooling sonocrystallization process, to recrystallize AP to control and modify its particle size and crystal habit. The effects of solution concentration, sonication intensity, sonication pulse on/off recipe, and cooling rate on the recrystallization of AP are first investigated using a Taguchi L9 orthogonal array design. By understanding the main effect of these operating parameters, further sonocrystallization experiments are designed for process improvement. Compared with the unprocessed AP, the crystal habit and mean particle size of AP are considerably modified after cooling sonocrystallization, achieving a mean size of approximately 50 µm with a regular habit. Consistency in crystal structure and spectrometric properties between sonocrystallized and unprocessed AP was confirmed. Furthermore, the thermal properties and decomposition behavior of the sonocrystallized AP are analyzed, revealing improved exothermic characteristics. These results prove that cooling sonocrystallization is an efficient tool for producing AP particles and also holds the potential for preparing fine particles of other energetic materials.

Glycine manganese sulphate (GMS) crystals are produced by a slow evaporation technique at room temperature. This is confirmed that triclinic of the crystal lattice system by using single crystal X-ray diffraction analysis and to determine the lattice parameters of the synthesised crystals. Powder XRD is used to confirm the planar indexing and crystalline structure. The Fourier Transform Infrared (FT-IR) spectra are examined to verify that functional groups are present in the generated GMS crystals. By establishing a cut-off wavelength of 253 nm, spectra of visible, near-infrared, and Ultra Violet (UV) light from 200 to 1100 nm are analyzed. At frequencies ranging from 100 Hz to 8 MHz, the grown crystal's dielectric response is studied. Vickers microhardness tester is utilized to find out how strong the grown crystal is mechanically. Photoluminescence (PL) investigations often aim to detect crystal formation faults and contaminants. Etching analysis is used to find surface flaws and dislocations on the formed crystal's surface. The internal surface property of the produced crystal is investigated with scanning electron microscopy (SEM). The findings contradicted each other, suggesting that the created GMS crystal be used in opto-electronic device applications.

Optically transparent metal semi organic single crystal of 1,4-diazabicyclo[2.2.2]octane-1,4-diium tris(nitrato)-silver (DTNS) is synthesized using slow evaporation solution technique. This single crystal is grown with dimension up to $��3�\times �0.6�\times �0.2���{\mathrm{cm}}^3�$ using 1,4-diazabicyclo[2.2.2]octane (DABCO) as solute and water and methanol as solvent in the presence metal salt silver nitrate. Single crystal X-ray diffraction (XRD) study showed a trigonal structure with space group P3c1 and the sum formula $��C_6�H_{14}�A�g�N_5�O_9�$. The composition of metal Silver (Ag) in single crystal is confirmed through Energy Dispersive X-Ray Analysis. The confirmation of various functional groups in DTNS molecular structure is characterized by Fourier Transform Infrared Spectroscopy (FT-IR). UV–Visible absorption study showed the cut-off wavelength at 250 nm with transparency 350–700 nm and the bandgap is about 3.3 eV. The thermal stability and melting point temperature is analyzed by Thermogravimetry-Differential Scanning Calorimetry (TG/DSC). The third order Non Linear Optics (NLO) efficiency of the synthesized crystal is $��2�\times �{10}^6�$ times greater than that of KDP. All of these analysis implies that DTNS crystal can be beneficial element for non-linear optical applications.