Narrow Results

We have examined the deposition of highly conductive boron-doped microcrystalline silicon (μc-Si:H) films for application in solar cells. Depositions were conducted in a very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) chamber. In the deposition processes, various substrate temperatures (T_S) were applied. Highly conductive p-type microcrystalline silicon films were obtained at substrate temperature lower than 210°C. The factors that affect the conductivity of the films were investigated. Results suggest that the dark conductivity, which was determined by the Hall mobility and carrier concentration, is influenced by the structure. The properties of the films are strongly dependent on the substrate temperature. With T_S increasing, the dark conductivity (σ_d) increases initially; reach the maximum values at certain T_S and then decrease. Also, we applied the boron-doped μc-Si:H as p-layers to the solar cells. An efficiency of about 8.5% for a solar cell with μc-Si:Hp-layer was obtained.

The crystallization and sintering process of RuO${}_2\cdot$xH₂O nanoparticles have been investigated in this paper. The effect of RuO₂ crystallinity and particle size on the sheet resistance of RuO₂-based resistor paste after being co-fired with CaO–B₂O₃–SiO₂ green tapes has been reported. The results show that the nanoparticles are not fully crystallized below 600${}^{\circ }$C, and the effect of high-density defects, such as grain boundaries and dislocations on the residual resistance ($R_r)$ of RuO₂ particles, is significant. So, the sheet resistance decreases with the increase of crystallinity and the weakening of electron wave scattering. Above 600${}^{\circ }$C, the effect of crystal imperfections on $R_r$ is greatly weakened. However, the number of conductive chains formed in co-fired resistor decreases with the increase of particle size, thus the sheet resistance gradually raises. When the dwelling time is increased to 3 h, the RuO₂ is mostly crystallized and the effect of crystal imperfections on $R_r$ is negligible, and the sheet resistance mainly depends on particle size of RuO₂. Using RuO₂ particles with low crystallinity, small size and narrow particle-size distribution as conductive phase is expected to solve the problem of poor sheet resistance uniformity in high resistance paste for LTCC application.

In this paper, PE100 pipes with the diameter of 200 mm and the thickness of 11.9 mm were used as material. The welded joints were obtained in different welding pressures with the optimal welding temperature of 220${}^{\circ }$C. Reheating process on the welded joints with the temperature of 130${}^{\circ }$C was carried out. The joints exhibited X-type, and the cause of X-type joints was discussed. The temperature field in the forming process of welded joints was measured, and tensile and bending tests on welded joints were carried out. The fracture surface of welded joints was observed by scanning electron microscopy (SEM), and crystallinity calculation was taken by X-ray diffraction (XRD). The mechanism of X-type weld profile effects on welded joints properties was analyzed. It was concluded that the mechanical properties of welded joints decrease with the reduced X distance between lines.

In this work, a pulsed laser deposition (PLD) technique with an Nd:YAG laser source was used to produce pure Hydroxyapatite (HA) and Cu-substituted HA (Cu-HA) coatings on stainless steel substrates in vacuum at room temperature. It is observed that the combined effects of percentages of Cu dopants and laser energy as well as annealing temperature significantly modify the crystallinity of the films. The morphology and structural properties of the deposited HA films were analyzed by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Raman spectroscopy. FESEM images displayed various shapes of nanoparticles with high-surface density throughout the area of the substrate and with typical sizes around 26–208 nm. XRD analysis confirmed that post-deposition annealing is essential to achieve the desired crystallinity and uniformity of coatings. The Raman spectrum of HA has peaks at 958.22, 437.48, and 587.05 cm${}^{-1}$ attributed to the ${\nu }_1$ PO${}_4^{3-}$, ${\nu }_2$ PO${}_4^{3-}$, and ${\nu }_3$ PO${}_4^{3-}$, respectively. The synthesized HA and Cu-HA crystalline films are nanostructures with dense and compact microstructures. Finally, irregular surface and crystalline structure of fabricated films lead to the extension of the surface and enhance the cell’s proliferation in medical uses and biomedical applications.

Bonding performance of carbon fiber/polyetherketoneketone (CF/PEKK) laminates is closely related to crystallinity and is influenced by growth, formation, and density of spherulites. Press consolidation, with its ability to adjust pressure, exhibits superior quality compared to oven consolidation. However, bonding and production of CF/PEKK laminates using Press consolidation exhibit significant variations in quality depending on forming conditions. While research on producing CF/PEKK laminates using press consolidation is currently active, there is a lack of studies on co-consolidation for CF/PEKK laminates. Thus, in this study, establishment of forming process variables for press consolidation was conducted to achieve excellent bonding performance for CF/PEKK. Furthermore, IR heating-assisted surface heat treatment was employed to enhance bonding performance of CF/PEKK laminates by controlling crystallinity and spherulites. To analyze bonding performance, short bean shear testing was conducted to obtain interlaminar shear strength (ILSS). Results showed that surface modification through IR heating led to an increase in crystallinity and a noticeable growth in size of spherulites. In specific conditions, improved bonding performance was observed. This is judged to be primarily due to increase in spherulite size and crystallinity at bonding interface, attributed to specific conditions of both surface treatment through IR heating and Press consolidation.

Electrosorption of carbon nanotube and nanofiber (CNT–CNF) composite film electrodes was studied as a new desalination technology. The CNT–CNF composite film electrodes were grown on nickel sheets by low pressure thermal chemical vapor deposition. Different growth conditions at different acetylene flow rates of CNT–CNF composite film electrodes have been performed to obtain different crystallinities. The electrosorption experiments and Raman spectra analysis show the successful removal of ions with CNT–CNF composite film electrodes, depending on the optimal degree of crystalline perfection. In our work, optimal electrosorption was realized for the CNT–CNF composite film electrodes growing at 550°C with the acetylene and hydrogen flow rates of 30 and 200 sccm.

The Poly(vinylidene) fluoride (PVDF) thin films with a high content of β-phase were prepared by controlling heat-treatment temperature using casting from the poled solvents. The crystallite microstructure of thin films was depicted by the techniques of X-ray diffraction and FTIR. The results showed that heat treatment was favorable for inducing the β- and γ-phase formation of PVDF. The β phase films were obtained with heat treatment at temperatures ranging from 60°C to 120°C and annealing at 120°C after casting from DMF. The thermo-optical effect of β phase PVDF films was investigated using a spectroscopic ellipsometer. At temperatures ranging from 20°C to 100°C, the refractive index of PVDF was negatively correlated with the temperature between 350 and 1500 nm. The value of the t.o. coefficient of PVDF films was calculated at all temperatures. The maximum value of the t.o. coefficient was about 3.3 × 10^-4/°C at the ascending stage of temperature and 3.0 × 10^-4/°C at the descending stage of temperature. Therefore, it is possible to use the thermo-optic effect of the β phase PVDF for long wavelength infrared imaging.

Antimony doped tin oxide (ATO) nanoparticles were prepared by wet chemical coprecipitation method with different contents of polyvinyl alcohol (PVA) dispersant. The prepared ATO nanoparticles have been characterized by means of XRD, SEM, HRTEM, SAED, EDS, bulk density and electrical resistivity measurement. Results indicated that the approach functionalized by PVA dispersant enables a synchronous improvement of two important properties namely the dispersibility and electrical conductivity due to the mechanism of avoiding the formation of agglomeration of nanoparticles, which could be regarded as primary factors for the enhanced electron transfer of powders: The surface area over which are crucial for the interfacial arrangement and electron charge scattering/transfer processes. The bulk density and electrical resistivity decreased to a minimum of 0.90 g/cm³ and 1.44 Ω⋅cm at PVA dispersant content of 5%, and increased rapidly at higher PVA contents. The prepared ATO nanoparticles can serve as a kind of effective conductive filler in insulating species such as plastics, textile and rubber.

Nanohybrid thin films of titania-polymethyl methacrylate (TiO₂-PMMA) with varying degrees of nanocrystallinity have been successfully synthesized via an in-situ sol gel-polymerization route, assisted by subsequent thermal and water vapor treatments. Post-hydrothermal treatment by water vapor at relatively low temperatures led to a higher degree of crystallinity for TiO₂ nanoparticles than the conventional thermal annealing. The degree of TiO₂ crystallinity in the resulting nanohybrid films was studied by using XRD, FTIR, UV-Vis spectroscopies and HRTEM. The resulting nanohybrid thin films are highly transparent in the visible region, with an estimated band gap energies, E_g, close to that of anatase TiO₂ (~ 3.20 eV). The nanocrystallinity level of TiO₂ phase strongly affects both linear and nonlinear optical properties of the nanohybrids. A significant enhancement in linear refractive index, n_o, up to 1.780 and a third-order nonlinear optical susceptibility, χ⁽³⁾ as high as 5.27 × 10^-9esu, were demonstrated with the nanohybrid exhibiting the enhanced TiO₂ crystallinity and well-preserved PMMA matrix.

The orientation and crystallinity evolution of isotactic polypropylene (iPP) induced by rolling were studied using wide angle X-ray scattering with an area detector. The tensile mechanical properties of rolled isotactic polypropylene sheets were also measured in this work. The texture component method was used to analyze the rolling texture. The rolling texture consists mainly of (010)[001], (130)[001] and [001]//RD fiber components in the sample with a rolling true strain of 1.5. The results reveal that crystallinity drastically decreases during rolling. It is suggested that amorphization is a deformation mechanism which takes place as an alternative to crystallographic intralamellar slip depending on the orientation of the lamellae. Both the orientation and crystallinity affect the tensile mechanical properties of rolled polypropylene. Crystallinity influences the elastic modulus on both directions and yield strength on transverse direction at the first stage of deformation. Orientation is the main reason for the changes of mechanical properties, especially at the latter part of deformation. The changes of both tensile strength and elongation percentage on rolling direction are larger than those on transverse direction, which results from the orientation. At last, the anisotropic mechanical properties occur on the rolling and transverse direction: high tensile strength with low elongation percentage on rolling direction and low tensile strength with high elongation percentage on transverse direction.

Fluoropolymer blends have been widely used as binders for exterior coatings because of their excellent resistance to ultra-violet (UV) radiation as well as to many corrosive chemical agents. It is known that the fluorinated component usually has a lower glass transition temperature and easily crystallizes in the final structure depending upon the blend composition and sample annealing condition. We investigated the effect of blend composition and annealing process (slow and fast cooling) on the surface morphology and microstructure a poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blend before and after UV exposure. Surface and subsurface microstructures were studied by atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM). Bulk microstructure of PVDF-coatings before and after UV exposure were characterized using small angle neutron and light scattering. Higher PVDF content and a slow cooling process result in larger spherulite crystallite structure and rougher surface morphology. Significant ordering in the spherulite crystallite structure has been observed on the surface and the bulk films after UV exposure.

The dependence of polarization fatigue on crystallinity of vinylidene fluoride and trifluoroethylene copolymer films was studied. Experimental data indicated that the higher the crystallinity of the film was, the slower the fatigue rate of the film became. A possible explanation was put forward, and it was regarded that the space charges, trapped at the boundaries of crystallites and/or captured by the defects lying both in amorphous and crystalline phases, should make the major contribution to polarization fatigue.

It is important to reduce costs and improve performance by microstructure-control of materials. The direct precipitation method and hydrothermal method were adopted to adjust the crystallinity of zinc tungstate (ZnWO₄) pigments. Correlation between the crystallinity of ZnWO₄ and its anti-corrosion performance is explored. The results confirm that ZnWO₄ crystals prepared by hydrothermal reaction for 12 h have high crystallinity, and the corrosion resistance is enhanced by 737.0% compared with blank coating in the epoxy resin system. The improvement in corrosion inhibition is due to the enhancement of the shielding effect of the multilayer passivation film and electronic suppression effect resulted from the high ZnWO₄ crystallinity. The low ZnWO₄ crystallinity can weaken the corrosion resistance because of the defect-enriched effect. Advancement in anticorrosive performance by crystallinity-control meets the reduction of costs and energy consumption in the coatings industry.

α-MnO₂ electrode materials with sphere-, rod- and flower-like nanostructures were for the first time fabricated by a redox reaction between KMnO₄ and NaHSO₃ in chemical bath. Crystal structure and morphology of the as-crystallized samples were characterized by X-ray diffraction and scanning electron microscopy. The influence of reaction temperature and H⁺ concentration on both morphology and crystalline nature was investigated. Their electrochemical behaviors were investigated by cycling voltammetry and galvanostatic charge/discharge measurements in a three-electrode glass cell. Depending upon different synthesis conditions of α-MnO₂ electrodes, their specific capacitance values varied in the range of 43 to 197 F g^-1 at the current density of 1 A g^-1. Moreover, their specific capacitance values decrease with increasing crystallinity and particle size. In this work, we conclude that the energy storage mechanism is closely related to the particle aggregation state of electrode materials.

NiTi shape memory alloys were subjected to a single step severe plastic deformation via the equal channel angular pressing (ECAP). The properties were analyzed by comparing the transformation characteristics for sections across the thickness of the deformed sample, with focus on the deformation gradient in the outer layers of the materials and the front surface that gradually engages in the deformation. A gradient related to the crystallinity and the state of stress was observed across the thickness of the deformed sample.

Fe₃O₄ nanoparticles were synthesized by a facile hydrothermal method using triethanolamine. Effects of reaction times (2–8h) on crystallinity and electrochemical performances of Fe₃O₄ were investigated. Samples were analyzed by X-ray diffraction, infrared spectroscopy, N₂ adsorption–desorption, scanning electron microscope, galvanostatic charge/discharge, and cyclic voltammetry. Results showed that the crystallinity of Fe₃O₄ was increased with hydrothermal time, and the sample prepared at 2h displayed amorphous structure with small grain size and large surface area of 165.0m²g${}^{-1}$. The sample exhibited typical pseudocapacitive behavior with capacitance of 383.2Fg${}^{-1}$ at 0.5 Ag${}^{-1}$ in Na₂SO₃ electrolyte. After 2000 cycles, the capacitance retention of Fe₃O₄ at 2h was recorded as 83.6%, much higher than 26.3% for sample at 8h. It indicated that hydrothermal method was an effective approach to obtain amorphous Fe₃O₄, implying the potential application for preparing metal oxide electrode for supercapacitors.

In this work, we investigated the morphology and crystallinity changes of a $\beta$-ketoenamine COF, Tp-BD(Me)₂ (Tp=1,3,5-triformylphloroglucinol, BD(Me)₂=3,3^′-dimethyl-[1,1^′-biphenyl]-4,4^′-diamine), with different reaction time and temperatures. Powder X-ray diffraction (PXRD) and Fourier-transform infrared (FTIR) spectra tests confirmed the synthesis of Tp-BD(Me)₂, which has a specific $\beta$-ketoenamine linkage and a probable eclipsed stacking mode. At a reaction temperature of 50^∘C, the morphology of Tp-BD(Me)₂ underwent a progressive process of growing, extending and splitting. The band gaps of the Tp-BD(Me)₂ obtained with the reaction time of 18–24 h were calculated near 2.0 eV. The BET surface areas of the Tp-BD(Me)₂ were around 400–600 m²/g. It is not an optimal choice if the reaction temperature is below 50^∘C, which could cause a low crystallinity and disordered morphology. However, slightly improving the reaction temperature to 60^∘C is beneficial for generating high-crystallinity Tp-BD(Me)₂.

Hydroxyapatite (HAp) was synthesized in the presence of various types of amino acids; glycine (Gly), alanine (Ala), arginine (Arg), aspartic acid (Asp) and glutamic acid (Glu), as components of proteins, in order to investigate their effects on hydroxyapatite crystals. Glycine and alanine are neutral, arginine is a basic and aspartic acid and glutamic acid are acidic amino acids. Furthermore, we estimated the crystallinity and solubility of synthesized HAp. Analysis of X-ray diffraction demonstrated that all of the synthesized HAp had a typical X-ray diffraction patterns of HAp, whereas the crystallinity of HAp synthesized in the presence of either aspartic acid (HAp_Asp) and glutamic acid (HAp_Glu) decreased with the increase of the amounts of these acidic amino acids present. The solubility of HAp_Asp and HAP_Glu increased sigiificantly with the increase of the amounts of acidic amino acids present. The lower crystallinity of HAp_Asp and HAp_Glu observed in the current study was likely due to the adsorption of these amino acids on HAp. These results suggest that amino acids may play a major role in the regulation of crystallinity and solubility of HAp which is frequently used as a biomaterial for hard tissue diseases management.