Crystal Thermal Behavior Research Articles

Silk I and Silk II studied by fast scanning calorimetry.

Silkworm silk is a naturally occurring biomaterial. The fibroin component of silk forms two types of crystals. Silk properties depend upon the amount and type of crystals, and their stability. One measure of stability is crystal melting temperature. Crystals which are more stable have a higher melting temperature. Until now, it has been challenging to study thermal behavior of silk crystals because they degrade at high temperature. To avoid degradation, and study the melting properties of silk biomaterial, we heated silk at a very fast rate of 2000K/s using a special calorimeter. We have shown that the two crystal types have very different melting temperatures, indicating that one crystal type is much more stable than the other.

Influence of bis-thiourea nickel nitrate on the structural, optical, electrical, thermal and mechanical behavior of a KDP single crystal for NLO applications

A single crystal of bis-thiourea nickel nitrate (BTNN) doped potassium dihydrogen phosphate (KDP) has been grown from solution at room temperature by a slow evaporation technique. The cell parameters of the grown crystals were determined using single crystal x-ray diffraction analysis. The different functional groups of the grown crystal were confirmed using Fourier transform infrared analysis. The improved optical parameters of the grown crystal have been evaluated in the range of 200–900 nm using UV–visible spectral analysis. The grown crystal was transparent in the entire visible region and the band gap value was found to be 4.96 eV. The influence of BTNN on the third order nonlinear optical properties of KDP crystal has been investigated by means of the Z-scan technique. The second harmonic generation (SHG) efficiency of grown crystal measured using a Nd-YAG laser is 1.98 times higher than that of pure KDP. The third order nonlinear optical susceptibility (χ3) and nonlinear absorption coefficient (β) of BTNN doped KDP crystal is found to be 1.77 × 10−5 esu and 5.57 × 10−6 cm W−1 respectively. The laser damage threshold (LDT) energy for the grown crystal has been measured by using a Q-switched Nd:YAG laser source. The bis-thiourea nickel nitrate shows authoritative impact on the dielectric properties of doped crystal. The influence of bis-thiourea nickel nitrate on the mechanical behavior of KDP crystal has been investigated using Vickers microhardness intender. The thermal behavior of BTNN doped KDP crystal has been analyzed by TGA/DTA analysis.

Crystallization of interphase droplets in emulsion explosive matrices

ABSTRACTThe instability of emulsion explosive matrices is mainly due to the crystallization of interphases as oversaturated aqueous solutions of nitrate salts. The principal features of crystallization for this type of emulsion have been previously studied; however, there is no consensus regarding the mechanism of crystallization for an emulsion explosive matrix. This study is devoted to the investigation of the crystallization behavior of interphase droplets. By monitoring the mass change of emulsions during their aging process, it was found that the mass of the emulsions remains almost constant and that water still completely existed in the emulsion system after crystallization of the interphase droplets. The ammonium nitrate (NH4NO3) crystals in the emulsion explosive matrices were then separated successfully using a simple method. The thermal behavior of pure NH4NO3 and crystals in the emulsion explosive matrices was studied by differential scanning calorimetry-thermogravimetric analysis (DSC-TG) at a heating rate of 10 K/min. The experimental results show that the thermal behavior of the crystals in the emulsions was exactly the same as for pure NH4NO3, meaning that only NH4NO3 crystallized from the emulsion explosive matrices with no water crystals. Thus, it could be concluded that after crystallization of the dispersed drops in the emulsion explosive matrices, pure NH4NO3 crystals and new smaller droplets were produced.

First principles calculation of thermal expansion coefficients of pure and Cr doped α-alumina crystals

We have performed theoretical analysis of thermal expansion behavior of alumina crystals under finite temperature based on first principles phonon state calculations. Liner thermal expansion coefficients of a pure α-alumina crystal have been evaluated based on quasi-harmonic approximation including crystalline anisotropy. The Cr doping effect on the alumina crystal has also been examined and found that the doping can cause a noticeable change on the thermal expansion coefficient. The present results demonstrate that the first principles theoretical approach can be helpful for reproducing or predicting thermal expansion behaviors including dopant effects, which may pave a way for possible control of thermal expansion of materials by doping or alloying.

Synthesis, growth, structural, optical, thermal, dielectric and mechanical studies of piperidinium p-nitrophenolate single crystals

Abstract A novel single crystal of piperidinium p-nitrophenolate (PPNP) was successfully grown by slow evaporation solution growth technique at constant temperature (308 K) with dimension 40 × 5 × 3 mm3. The structure parameters of grown crystal were confirmed from single crystal X-ray diffraction studies. Infrared, Raman and NMR spectral analyses were used to elucidate the functional groups present in the compound. UV–vis spectral studies indicate that the grown crystal is transparent in the entire visible region with a lower cut off wavelength of 505 nm. Photoluminescence spectral study revealed the transition mechanism of ions. Thermal analysis was carried out to study the thermal behavior of PPNP crystal. The powder second harmonic generation test confirmed the nonlinear optical behavior of grown crystal. The dielectric loss and dielectric constant as a function of frequency and temperature were measured for the grown crystal. The mechanical strength of the crystal was estimated by Vicker's hardness test.

Thermal expansion behavior of A- and B-type amylose crystals in the low-temperature region

The thermal expansion behaviors of A-type and B-type amylose crystals, which were prepared by recrystallization of short amylose chains synthesized by phosphorylase, were investigated using synchrotron X-ray powder diffraction between 100 and 300K. For both types of crystals, the room-temperature phase (RT phase), which is the usually observed phase, transitioned to a low-temperature phase (LT phase), on cooling. The phase transitions took place reversibly with rapid changes in the unit-cell parameters around 200–270K. The differences between the RT and LT phase were investigated using solid-state 13C NMR spectroscopy, which revealed there were changes in molecular chain conformations. These results suggest that the phase transition of water molecules on the crystalline surfaces affects the thermal behavior and structure of polysaccharide crystals.

Thermal decomposition of ammonium tetrathiotungstate

The thermal decomposition of ammonium tetrathiotungstate (ATT), (NH4)2WS4, was studied by SEM, FTIR, XRD, EDX and TG/DTA-MS. The decomposition of ATT involved three steps in inert atmosphere: (1) release of free water between 30 and 140 °C; (2) formation of an amorphous WS3 phase between 170 and 280 °C, from which (3) a slightly crystalline WS2 formed between 330 and 470 °C. As a difference compared to inert atmosphere, in air in the second step, the ATT decomposed into directly WS2 instead of WS3. This WS2 phase was amorphous and still contained traces of ATT. Between 260 and 500 °C from the WS2, monoclinic tungsten oxide crystallized in two steps: at 302 °C a slightly crystalline m-WO3 formed, which became more crystalline at 471 °C. During the investigation of the effect of the particle size, it was found that the thermal behaviour of ATT crystals was similar to ATT powder, with some shift in the decomposition temperature. The XRD results showed that the WS2 formed from the ATT powder in N2 had a higher level of crystallization, compared to the WS2 obtained from ATT crystals.

Synthesis, Preparation, and Characterization of Liquid Crystal/Organo-Montmorillonite Nanocomposites

A new chiral calamitic liquid crystal 4′-((S)-3,7-dimethyloctyloxy)phenyl 4-(10-undecen-1-yloxy)benzoate (DOPUB) has been synthesized and characterized by spectroscopic methods (1H-NMR and 13C-NMR). The focus is on the preparation of the nanocomposites of new chiral calamitic liquid crystal DOPUB/Organo-montmorillonite clay (OMMT) by solution intercalation method addition with OMMT contents 2.5, 5, and 7.5 wt% and determination of the morphology, thermal behavior, and crystalline properties of liquid crystal DOPUB/OMMT. Montmorillonite (MMT) modified by cationic surfactant cetyltrimethylammonium bromide (CTAB) for increasing the interaction of clay with DOPUB liquid crystal. The characterization of clay minerals and nanocomposites was investigated by X-ray diffraction. The mesomorphic behavior of liquid crystal (DOPUB) and the nanocomposites was investigated by differential scanning calorimetry (DSC) and optical polarizing microscopy (PM).

New insights into the thermal behaviour of organic ionic plastic crystals: magnetic resonance imaging of polycrystalline morphology alterations induced by solid-solid phase transitions.

Organic ionic plastic crystals (OIPCs) show strong potential as solid-state electrolytes for lithium battery applications, demonstrating promising electrochemical performance and eliminating the need for a volatile and flammable liquid electrolyte. The ionic conductivity (σ) in these systems has recently been shown to depend strongly on polycrystalline morphology, which is largely determined by the sample's thermal history. [K. Romanenko et al., J. Am. Chem. Soc., 2014, 136, 15638]. Tailoring this morphology could lead to conductivities sufficiently high for battery applications, so a more complete understanding of how phenomena such as solid-solid phase transitions can affect the sample morphology is of significant interest. Anisotropic relaxation of nuclear spin magnetisation provides a new MRI based approach for studies of polycrystalline materials at both a macroscopic and molecular level. In this contribution, morphology alterations induced by solid-solid phase transitions in triisobutyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1444FSI) and diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate (P1224PF6) are examined using magnetic resonance imaging (MRI), alongside nuclear magnetic resonance (NMR) spectroscopy, diffusion measurements and conductivity data. These observations are linked to molecular dynamics and structural behaviour crucial for the conductive properties of OIPCs. A distinct correlation is established between the conductivity at a given temperature, σ(T), and the intensity of the narrow NMR signal that is attributed to a mobile fraction, fm(T), of ions in the OIPC. To explain these findings we propose an analogy with the well-studied relationship between permeability (k) and void fraction (θ) in porous media, with k(θ) commonly quantified by a power-law dependence that can also be employed to describe σ(fm).

Synthesis, growth, structural and optical studies of a novel organic Piperazine (bis) p-toluenesulfonate single crystal

A novel organic single crystal of Piperazinium (bis) p-toluenesulfonate (PPTS) was grown by a slow evaporation solution growth technique. The structure of the grown crystal was determined using single crystal X-ray diffraction analysis. The PPTS crystal belongs to the triclinic crystal system with space group of P1¯. The presence of functional groups was confirmed by FTIR spectral analysis. The optical transmittance range and cut-off wavelength were identified by UV–vis–NIR spectral studies. The luminescent properties of PPTS crystal were investigated. The thermal behavior of PPTS crystal was studied by TG-DT analyses.

Experimental and theoretical investigations on N,N′-diphenylguanidinium dihydrogen phosphite – A semi-organic nonlinear optical material

Single crystal of N,N′-diphenylguanidinium dihydrogen phosphite (DPGP) was grown by a slow evaporation technique and was characterized by single crystal X-ray diffraction and powder X-ray diffraction to confirm the structure and crystalline nature of DPGP crystal. UV–vis spectral study revealed that the DPGP crystal is optically transparent. The chemical bonding and presence of various functional groups were confirmed by the FT-IR and FT-Raman spectral studies. The thermal behavior of DPGP crystal was analyzed by simultaneous TG-DTA studies. The laser induced surface damage threshold study was carried out for the grown crystal using Nd:YAG laser. The second harmonic generation (SHG) nonlinearity of the grown crystalline sample was measured by the Kurtz and Perry powder technique. The quantum chemical analyses were performed by density functional theory (DFT) using B3LYP/6-31G (d,p) basis set.

Dynamiclly Functional Materials Based on Hydrogen-Bonded Liquid Crystals

A new series of supramolecular hydrogen-bonded liquid cryatals complexes were synthesized based on pyridine derivative and 4-n-alkoxybenzoic acids. The formation of hydrogen bonds was verified by infrared spectra. The thermal behavior of supramolecular liquid crystals was studied using differential scanning calorimeter (DSC). The liquid crystal texture was revealed with polarizing optical microscope (POM). It demonstrats that all supramolecular complexes have good liquid crystal properties.

Synthesis, spectral analysis, optical and thermal properties of new organic NLO crystal: N,N′-Diphenylguanidinium Nitrate (DPGN)

A new organic NLO material N,N′-Diphenylguanidinium Nitrate (DPGN) single crystal was grown by slow evaporation technique using methanol as solvent. Single crystal X-ray diffraction and powder X-ray diffraction experiments were carried out in order to confirm the structure and crystalline nature of DPGN crystal. Wide band gap of 3.9eV with transmittance of 57% up to 800nm is observed for the grown crystal using UV–vis spectral analysis. The chemical bonding and presence of various functional groups were confirmed by the FT-IR and FT-Raman spectral studies. The thermal behavior of DPGN crystal was analyzed by simultaneous TG-DTA studies. The second harmonic generation (SHG) nonlinearity of the grown crystal was measured by Kurtz and Perry powder technique and was found to be comparable with that of the standard reference material potassium dihydrogen phosphate (KDP) crystal.

Determination of Melting Point of Polyethylene Based on Inverse Opal

The thermal tunable behavior of polyethylene inverse opal photonic crystals was investigated and the mechanism of this behavior was illustrated. Based on these researches, a method of determination of melting point was established. This principle of such method is that at the temperature of above the melting point, the molecular chain of the materials started to move and caused the destruction of the ordered nanostructure of the inverse opal. This destruction could be real-time monitored by the reflectance spectra. In addition, this process could also be observed by naked eyes because the structure color of the materials was also changed. Thus, the melting point of the materials could be detected by our method without using complex and expensive analyzer.

Beating the Heat - Fast Scanning Melts Silk Beta Sheet Crystals

Beta-pleated-sheet crystals are among the most stable of protein secondary structures, and are responsible for the remarkable physical properties of many fibrous proteins, such as silk, or proteins forming plaques as in Alzheimer's disease. Previous thinking, and the accepted paradigm, was that beta-pleated-sheet crystals in the dry solid state were so stable they would not melt upon input of heat energy alone. Here we overturn that assumption and demonstrate that beta-pleated-sheet crystals melt directly from the solid state to become random coils, helices, and turns. We use fast scanning chip calorimetry at 2,000 K/s and report the first reversible thermal melting of protein beta-pleated-sheet crystals, exemplified by silk fibroin. The similarity between thermal melting behavior of lamellar crystals of synthetic polymers and beta-pleated-sheet crystals is confirmed. Significance for controlling beta-pleated-sheet content during thermal processing of biomaterials, as well as towards disease therapies, is envisioned based on these new findings.

New Multicomponent Porous Architecture of Self-Assembled Porphyrins/Calixarenes Driven by Nickel Ions

A new multicomponent material with nanoporous structure has been synthesized by co-crystallization of a mixture of cationic meso-tetrakis(4-N-methylpyridyl)porphyrin (H2T4) and meso-tri(4-N-methylpyridyl)porphyrin (H2T3py) with polyanionic 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis(hydroxylcarbonylmethoxy)calix[4]arene (C4TsTc) in the presence of Ni2+ ions. The structural analysis indicates that the overall architecture is assembled by interpenetrated two-dimensional (2D) meshes where the nodes are built up by a central tetracationic H2T4 porphyrin with arms hosted in sulphonated rims of four cavitands. The approximately 2D square network is formed by Ni2+ ions bridging the calixarene carboxylate rims in a tail-to-tail fashion. The central H2T4 stacks with two external H2T3py molecules having the neutral pyridine arm N-coordinated to Ni2+ ions. These metal centers interconnect the orthogonal 2D meshes by further coordination of calixarene–carboxylate groups. Self-organization of the new multicomponent material, featuring large channels (60% of volume accessible to solvent molecules) and potential readily accessible metal active sites, has been driven by both supramolecular host–guest recognition and coordinative assembly. The thermal behavior of native and nickel-containing crystals was studied by hot stage microscopy and differential scanning calorimetry. The decomposition temperatures of the multicomponent materials, 465–470 °C, are about 100 °C higher than those of the single building blocks.

Growth, optical, thermal, and conductivity behavior of nonlinear optical single crystals of CdHg(SCN)4(CH3OC2H5O)

In this study, organometallic nonlinear optical single crystal of Cadmium mercury thiocyanate glycol monomethyl ether was grown by slow evaporation technique at room temperature. The grown crystal was confirmed by single crystal XRD and FT-IR analysis. Optical and thermal properties of the sample were investigated by UV–Vis–NIR, TG–DTA and DSC technique. Using Tauc’s relation, the band gap of the crystal was estimated as 3.99 eV. The thermal studies confirm that the CMTG is thermally stable up to 105 °C. Photoluminescence and ac & dc conductivity measurements of the sample were also carried out and reported for the first time. The PL analysis confirms the suitability of the material for application in the blue–green region. The temperature dependences of ac & dc conductivities of CMTG were investigated, and the activation energies were found to be 0.098 and 0.045 eV, respectively. The SHG efficiency measurement confirms that the NLO efficiency of CMTG is nearly three times more efficient than urea.

Growth and physical properties of a new crystal for NLO applications: Bisguanidinium hydrogen phosphate monohydrate (G2HP)

Single crystals of nonlinear optical material bisguanidinium hydrogen phosphate monohydrate (G2HP) belonging to non-centrosymmetric space group P4̄21c were successfully grown by the slow evaporation method. G2HP crystals of size 32×3×3mm3 were obtained in 20 days. Initially, solubility tests were carried out for three solvents such as water, water–methanol, water–ethanol. Among the three solvents, the solubility of G2HP was found to be the highest in water, so crystallization of G2HP was done from its aqueous solution. Morphological analysis reveals that the crystal is rectangular in shape with six developed faces with major face forms along {111}, {120} and {−110} crystallographic axes. As grown, crystals were characterized by X-ray powder diffraction studies, optical transmission spectral studies and laser damage threshold studies. Nonlinear optical (NLO) behavior of G2HP crystal was studied by Kurtz powder. Infrared spectroscopy, thermo gravimetric analysis and differential thermal analysis measurements were performed to study the molecular vibration and thermal behavior of G2HP crystals. Thermal analysis and micro hardness measurements for G2HP crystal were carried out. The chemical etching study was carried out using deionized water with ethanol (1:1) ratio as an etchant.

Thermal characterization of nanoscale phononic crystals using supercell lattice dynamics

The concept of a phononic crystal can in principle be realized at the nanoscale whenever the conditions for coherent phonon transport exist. Under such conditions, the dispersion characteristics of both the constitutive material lattice (defined by a primitive cell) and the phononic crystal lattice (defined by a supercell) contribute to the value of the thermal conductivity. It is therefore necessary in this emerging class of phononic materials to treat the lattice dynamics at both periodicity levels. Here we demonstrate the utility of using supercell lattice dynamics to investigate the thermal transport behavior of three-dimensional nanoscale phononic crystals formed from silicon and cubic voids of vacuum. The periodicity of the voids follows a simple cubic arrangement with a lattice constant that is around an order of magnitude larger than that of the bulk crystalline silicon primitive cell. We consider an atomic-scale supercell which incorporates all the details of the silicon atomic locations and the void geometry. For this supercell, we compute the phonon band structure and subsequently predict the thermal conductivity following the Callaway-Holland model. Our findings dictate that for an analysis based on supercell lattice dynamics to be representative of the properties of the underlying lattice model, a minimum supercell size is needed along with a minimum wave vector sampling resolution. Below these minimum values, a thermal conductivity prediction of a bulk material based on a supercell will not adequately recover the value obtained based on a primitive cell. Furthermore, our results show that for the relatively small voids and void spacings we consider (where boundary scattering is dominant), dispersion at the phononic crystal unit cell level plays a noticeable role in determining the thermal conductivity.

Theoretical study on thermal behavior of passively Q-switched microchip Nd:YAG laser

This study deals with the thermal characterization of a continuous wave (CW-) and end-pumped passively Q-switched microchip Nd:YAG laser crystal by solving the rate and heat transfer equations in the laser cavity. In this approach, a parametric study has been performed to investigate the influence of the pumping parameters, cooling metal dimension and also the crystal dimension and doping concentration on the thermal behavior of the laser crystal. Obtained results reveal a closed correlation between the mentioned parameters and the thermal behavior of the crystal indicating that a proper selection of the laser parameters is essential to control the crystal's temperature and improve the performance of the laser accordingly.