Table of Content

15 December 2021, Volume 50 Issue 12

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Research Articles

Gradient Doping YVO₄-Nd∶YVO₄ Composite Crystal

QIU Kebin, ZHUAN Naifeng, CHEN Xin, CHEN Weidong, ZHANG Ge, ZHAO Bin

2021, 50(12):  2205-2211. 

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A new YVO₄-Nd∶YVO₄ composite crystal was grown by a modified Cz method, a 0.10%~0.25%(atomic ratio) concentration gradient doping of Nd³⁺ in the middle part of the crystal was achieved. In the crystal, the weak absorption coefficient of the Nd³⁺ doped region is larger than that of the un-doped region, indicating the interface absorption phenomenon. By observing the absorption of the pump light by the composite crystal and temperature distribution in the crystal, it is found that the pumping absorption of the crystal along the axial direction is relatively uniform, and the temperature gradient in the crystal is relatively small. The uncoated composite crystal samples achieve well performance of CW laser at 1 064 nm, with a light-to-light conversion efficiency of 37.0% and a slope efficiency of 40.9%.

First-Principle Study on Structure and Thermodynamics Properties of Al_xGa_1-xN Nitride

LI Pengtao, WANG Xin, LUO Xian, CHEN Jianxin

2021, 50(12):  2212-2218. 

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With the help of CASTEP first-principles calculations, the different doping structures and thermal properties of the semiconductor Al_xGa_1-xN were carefully studied for better understanding the influence of the microstructure on the thermodynamic properties in group Ⅲ nitrides, and then provide data support during the design processes of ultra-high power devices. After the optimization of Al_xGa_1-xN structures, with the increase of Al composition (atomic fraction), the lattice constant, average bond length and lattice heat capacity linearly decreases. The calculation of properties results indicate that the introduction of Al component in GaN will introduce an impurity mode in the frequency band gap. As the concentration of Al component increases, the impurity mode widens and enters the low frequency range. The top frequency of the low frequency band increases with the increase of Al composition, and the top frequency of the low frequency band above 12.5% is larger than (1/2)A₁(LO). From 300 K to 700 K, at the fixed temperature, with the increase of Al composition, the heat capacity of Al_xGa_1-xN alloy linearly decreases. The result in this paper provides a useful reference for the design of Ⅲ-nitride semiconductor high-power devices, such as Al_xGa_1-xN.

β-Ga₂O₃ Films Growth on SiC Substrate and p-SiC/n-β-Ga₂O₃ Heterojunction Photovoltaic Properties

LUO Jianren, WANG Xianghu, FAN Tianyao, JIN Jiani, ZHANG Rulin

2021, 50(12):  2219-2224. 

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In this paper, β-Ga₂O₃ films grown preferentially along (403) were prepared on p-type 4H-SiC substrate by pulsed laser deposition (PLD). The results show that the growth temperature has an important influence on the morphology, structure, composition and growth mechanism of β-Ga₂O₃ film. When the growth temperature increases from 300 ℃ to 500 ℃, the crystalline quality of the β-Ga₂O₃ film raises with the increasing temperature, but when the temperature further increases to 600 ℃, the crystalline quality of the thin film becomes worse. It was tried to explain that the kinetic energy of atoms deposited on the substrate increases with the increase of growth temperature below 500 ℃, leading to easier migration of atoms, finally, the film is grown in two-dimensional mode and has smaller roughness as measured by AFM. However, when the temperature further increases to 600 ℃, the two-dimensional growth mode is changed to three-dimensional island shape, because of the difference in thermal expansion coefficient between 4H-SiC substrate and β-Ga₂O₃ thin film, resulted in the larger roughness. The photovoltaic conversion efficiency of heterojunction solar cell based on p-4H-SiC/n-β-Ga₂O₃ reaches 3.43% under standard test conditions.

Study on the Formation Mechanism of Al(In) Nanostructures on GaAs(001) by Droplet Epitaxy

WANG Yi, LI Zhihong, DING Zhao, YANG Chen, LUO Zijiang, WANG Jihong, GUO Xiang

2021, 50(12):  2225-2231. 

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The indium and aluminum droplets were simultaneously grown on GaAs (001) substrate by droplet epitaxy method. The morphology of the samples with different indium and aluminum components was characterized by atomic force microscopy (AFM), and the distribution of elements on the surface was observed by XPS and scanning electron microscope (SEM). Results show that the density of InAlAs nanostructures on the surface of mixed deposition decreases with the decreases of indium composition, while the size of individual nanostructures increases. The experimental results show that the density of surface InAlAs nanostructures after hybrid deposition decreases with indium component decreasing, while the size of individual nanostructures becomes larger. SEM and XPS test results prove that the indium on the surface is not all segregated due to the high substrate temperature. It is speculated from the experimental results that when indium & aluminum droplets are deposited on the surface, a mixed indium & aluminum droplet is formed. The formation of dips in the center of the nanostructures formed after complete crystallization of the droplets is mainly due to the downward etching of droplets.

First-Principles Study on Lattice Structure, Electronic Structure and Optical Properties of Group-Ⅳ SiGeSn Ternary Alloy

SUN Shengliu, HUANG Wenqi, ZHANG Lixin, CHEN Zhenyu, WANG Hao

2021, 50(12):  2232-2239. 

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SiGeSn ternary alloys are hot materials for making silicon-based lasers currently due to their larger lattice and bandgap variation range compared with Group-Ⅳ binary alloys. In this paper, the first-principles methods based on density functional theory (DFT) were used to comprehensively and accurately study the lattice structure, electronic structure and optical properties of SiGeSn. Combined with quasi-random approximation and hybrid functional band gap correction, the lattice constants, band structure, density of states and optical properties of Si_1-x-yGe_xSn_y with different concentrations were calculated. Firstly, the variation law of lattice constant and bowing factor of SiGeSn were studied, and the solving schemes for the problems caused by mismatch and compressive strains for GeSn binary alloys were provided. Secondly, the band structures of SiGeSn and GeSn alloys were comparatively studied, and the microscopic mechanism of the effects on bandgap when alloying Si in GeSn was analyzed. Finally, the optical properties of SiGeSn and GeSn alloys such as dielectric function spectrum, absorption coefficient, extinction coefficient, reflectivity, refractive index and emissivity were comparatively studied. The results show the variation law of the lattice constant bowing factor is consistent with that of the electronegativity difference for SiGeSn, and Si-p electronic state is the most important contribution to the change of band gap. Compared to GeSn alloy with the same Sn concentration, SiGeSn can maintain the direct band gap characteristics and its band gap and light absorption wavelength have a wider variation range. Therefore, compared with GeSn alloy, SiGeSn has greater potential and advantages in the field of broadening the application wavelength of silicon-based high-efficiency light sources and photodetectors.

Growth Comparative Analysis of Aluminum Nitride Crystal by PVT Method on Al Surface and N Surface

SHI Yuezeng, WANG Zenghua, CHENG Hongjuan, ZHANG Li, YIN Liying

2021, 50(12):  2240-2245. 

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For the growth of AlN crystal by PVT method in nitrogen environment, the growth rate is different due to the different surface chemical properties between Al-polar and N-polar. And differentiated growth behaviors were observed within these surfaces due to the disparate migration behaviors of atoms. AlN growth on Al and N surfaces were carried out under the same conditions, i.e., growth temperature, thermal gradients, pressure, seeds and in the same apparatus. With the purpose of evidently exhibiting the discrepancy of Al and N surfaces, an Al-N growth within one growth cycle was realized by turning half of the seed crystal. For the Al-polar growth, domain boundaries merely within the well-grown planes were found. While for the growth on N surface, morphologies with well-aligned steps were observed, and grain boundaries are covered by these steps at the secondary growth.The growth step of Al surface is smooth but obstructed by defects, and the domain development is obviously independent of each domain growth which were further observed by AFM. The growth step of N surface is not regular but more continuous than that of Al surface, and the continuous growth step (or step cluster) also appears at the original boundary of crystal domain. Consisted with the XRD results, it can be figured out that, N growth is an effective approach to obtain an improved crystalline quality for AlN seeds with lower crystallinity.

Preparation and Properties of Ce³⁺ Doped CsPbBr₃ Nanocrystals

XIA Donglin, FU Chencheng

2021, 50(12):  2246-2254. 

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The Ce³⁺ doped CsPbBr₃ nanocrystals were prepared by hot-injection method, the crystal phase structure, micro-morphology, chemical composition, light absorption performance, luminescence performance, fluorescence lifetime and optical efficiency of luminescent solar concentrators (LSC) devices were characterized by XRD, TEM, XPS, UV-Vis, PL, Time-resolved fluorescence spectroscopy and J-V curve test. The experimental results show that the cubic phase Ce³⁺-doped CsPbBr₃ nanocrystals with good dispersion and average grain size of 12.26 nm are successfully prepared by hot-injection method. The optical band gap and fluorescence emission peak intensity of Ce³⁺ doped CsPbBr₃ nanocrystals shows a trend of increasing and then decreasing with the increase of Ce/Pb molar ratio. When n(Ce)/n(Pb)=0.25, the optical band gap reaches a maximum of 2.416 eV, the luminescence intensity is the strongest, and the fluorescence emission peak blue-shifts from 515 nm to 510 nm for pure CsPbBr₃ nanocrystals. The luminescence performance and stability of Ce³⁺ doped CsPbBr₃ nanocrystals are enhanced. The optical efficiency ηopt of Ce³⁺ doped CsPbBr₃ nanocrystals with polystyrene solution for the preparation of composite thin-film LSC is up to 6.81%.

Structural Characteristic and Elastic Property of ReB₂ under High Pressure

ZHANG Lihong, LEI Huiru

2021, 50(12):  2255-2261. 

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The structural characteristic and elastic property of ReB₂ in P6₃/mmc structure (hP6-ReB₂) were computed using the pseudopotential plane-wave methods based on the density functional theory. The equilibrium structural parameters of hP6-ReB₂ were calculated and its stability was verified thermodynamically, dynamically, and mechanically. It is found that the elastic constants, aggregate moduli increase as the pressure increases, and the Poisson ratio σ of hP6-ReB₂structure shows its brittleness, and the elastic waves reveals its elastic anisotropy. In addition, the obtained Vickers hardness of hP6-ReB₂ is 38.2 GPa. The density of electronic states reveals that there is a strong covalent bond between Re-B and B-B of hP6-ReB₂, and the covalent bond increases gradually with the increase of pressure.

Preparation and Luminescent Properties of Orange-Red Phosphors Ca₂GdNbO₆∶Sm³⁺, Na⁺

ZHANG Xin, CUI Ruirui, YUAN Gaofeng, DENG Chaoyong

2021, 50(12):  2262-2268. 

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In order to study the effect of Na⁺ doping on the luminescence of Ca₂GdNbO₆∶0.03Sm³⁺ phosphors, a series of Ca₂GdNbO₆∶0.03Sm³⁺, xNa⁺ (x=0.01, 0.03, 0.05, 0.07, 0.10; x is mole fraction) phosphors were successfully synthesized by high-temperature solid-state reaction. XRD patterns and the corresponding refinement results show that Na⁺ were successfully doped into Ca₂GdNbO₆∶0.03Sm³⁺ lattices. The luminescent properties of Ca₂GdNbO₆∶0.03Sm³⁺, xNa⁺ phosphors illustrate that the introduction of Na⁺ effectively improves the luminous intensity of Ca₂GdNbO₆∶0.03Sm³⁺ phosphors. Under the 406 nm excitation, the optimum doped concentration of Na⁺ is 5%, as well as the phosphors emit orange-red light with the strongest emission peak at 602 nm (⁴G_5/2→⁶H_7/2). The calculation of the concentration quenching and the thermal stability of Ca₂GdNbO₆∶0.03Sm³⁺, 0.05 Na⁺ host show that the energy transfer in the matrix occurs mainly among the nearest neighbor ions, and the thermal activation energy is 0.119 eV. The calculated color coordinate (0.593 5, 0.404 7) of the phosphors is located in the orange-red region, which is close to the standard (0.666, 0.333) specified by the international commission on illumination, indicating Ca₂GdNbO₆∶0.03Sm³⁺, xNa⁺ phosphors have potential application prospects in the field of white LEDs.

Preparation and Photoluminescence Properties of Red-Emitting Phosphor Gd₂ZnTiO₆∶Eu³⁺,Li⁺ under Near-UV Light Excitation

ZHANG Wangxiyue, ZHOU Qi, ZHOU Hengwei, JIANG Xiaokang

2021, 50(12):  2269-2275. 

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A series of Eu³⁺ doped and Li⁺, Eu³⁺ co-doped Gd₂ZnTiO₆ (GZT) red-emitting phosphors were successfully prepared by sol-gel method. The effects of Li⁺ and Eu³⁺ ions doping on the crystal structure, microstructure and luminescent properties of the samples were studied. Results show that the obtained double perovskite Gd₂ZnTiO ₆∶Li⁺,Eu³⁺(GZT∶Li⁺,Eu³⁺) phosphors crystallized in the monoclinic space group P2₁/n and are composed of irregular particles with the size of 10 μm. Under the excitation of 395 nm near ultraviolet light, the emission spectrum of GZT∶Eu³⁺ shows a typical linear characteristic spectrum of Eu³⁺ ions. The center position of the emission peak is located at 615 nm, which belongs to the ⁵D₀→⁷F₂ transition of Eu³⁺. The optimum doping concentration of Eu³⁺ is 0.07 (mole fraction). The obtained samples show obvious concentration quenching effect, and its mechanism can be identified as the electric dipole-dipole interactions(d-d). In addition, it is also found that Li⁺ doping has no effect on the crystal structure and micro morphology of the samples, but a certain amount of Li⁺ doping can significantly enhance the fluorescence intensity of the samples. When the concentration of Li⁺ is 0.05, the intensity of the main emission peak of the phosphor is the largest, which is 4.3 times of the original, indicating that high brightness GZT red-emitting phosphor can be obtained by co-doping Li⁺ and Eu³⁺. The CIE color coordinates of GZT∶0.14Eu³⁺,0.05Li⁺ phosphor is located at (0.631 1,0.375 3) close to the standard red color coordinates (0.670, 0.330), which is a potential red-emitting phosphor for LED.

Site Occupation and Luminescence Properties of Ce³⁺ Activated NaSr₄(BO₃)₃ Phosphors

MIAO Yuhao, WANG Weihao, WANG Yanhui, LUO Jiacheng, LAN Xuan

2021, 50(12):  2276-2282. 

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A series of Na_1+xSr_4-2x(BO₃)₃∶xCe³⁺ phosphors which can be excited by ultraviolet light were prepared by high temperature solid phase method. The phase structure, morphology and luminescence characteristics of the samples were characterized and analyzed by X-ray diffraction, scanning electron microscopy and fluorescence spectrum. X-ray diffraction results show that Ce³⁺ is successfully doped into NaSr₄(BO₃)₃. It is found that luminescence center of Ce³⁺ occupied Sr²⁺(1) and Sr²⁺(2) in NaSr₄(BO₃)₃ by means of Gaussian peak fitting and contrastive analysis of multiple spectra. The effects of Ce³⁺ doping concentration on the luminescence location and luminescence intensity were studied. With the increase of Ce³⁺ doping concentration, the emission spectra show a red shift and the luminescence intensity shows a trend of enhancing→weakening→re-enhancing. By comparing the emission spectra of phosphors with the absorption spectra of plant photosynthetic pigments, it is found that the phosphors can not only absorb 300~350 nm UV light, but also well cover the absorption band of blue light region required by plant photosynthetic pigments. This results show that the phosphor has potential value in agricultural production as a light conversion agent.

Structure and Properties of Ni(Ⅱ) and Cu(Ⅱ) Metal Complexes Coordinated by Two Ligands

DAI Siyu, LIU Yuqi, LI Yanghua, WANG Xinying, LI Wei, ZHANG Qingqing

2021, 50(12):  2283-2292. 

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In this paper, two coordination polymers containing imidazole ligands and dicarboxylic ligands were prepared by hydrothermal synthesis method: {Ni(nip)(p-bix)(H₂O)₂}_n (1) and{Cu(bbi)(dgc)}_n (2) (nip = 5-Nitroisophthalic acid; p-bix=1,4-Bis(imidazolyl-1-methyl)benzene; bbi=1,1’-(1,4-Butanediyl)diimidazole; dgc=3,3-Dimethylglutaric acid). The complexes were characterized by X-ray single crystal diffraction, elemental analysis, PXRD and TGA. The results show that the complex 1 is an one-dimensional double-stranded structure with a regular and ordered pore structure, and the nitro group (—NO₂) of 5-nitroisophthalic acid (nip) in the pore structure endows metal-organic frame (MOF) with potential application value. Futhermore, it is further extended into a 3D supramolecular architecture via strong hydrogen bonding interactions. While complex 2 featured a 3D network with a 4-connecte {6⁵·8} topological structure, and two mixed ligands of imidazole derivative ligand (bbi) and carboxylic acid ligand (H₂dgc) spirally coiled out an regular pore structure. It was rather remarkable that there are also abundant hydrogen bonds in the structure, which consolidate its 3D framework. In addition, the magnetic property of the two complexes was also investigated at 2 K to 300 K with an external magnetic field of 1 000 Oe and magnetic susceptibility datas were rationally fitted with the Curie-Weiss Law in the measured temperature range with θ=1.73 K and 6.78 K, respectively, indicating weak ferromagnetic interactions among metal ions in two complexes.

Synthesis, Crystal Structure and Theory Studies of a Cobalt Complex with Anion-Water Cluster

LI Huiling, YANG Min, SUN Jin, LI Rongchun, WEI Rongmin

2021, 50(12):  2293-2299. 

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Water clusters in metal complexes provide an effective way for the study on water in a macroscopic sense and water molecules related to protein molecules. In this paper, a supramolecular complex: [Co(2,2-bipy)₂(N₃)₂](N₃)_0.5Cl_0.5·2H₂O (1, 2,2-bipy=2,2-bipyridine) containing an anion-water cluster was synthesized using 2,2-bipyridine and azide ion as ligands. Single crystal X-ray diffraction analysis reveals that complex 1 crystallizes in triclinic, P-1 space group with a=0.822 54(7) nm, b=1.175 58(9) nm, c=1.237 06(10) nm, α=91.379 0(10)°, β=92.151 0(10)°, γ=108.119 0(10)°, V=1.135 27(16) nm³, and it is composed of a mononuclear [Co(2,2-bipy)₂(N₃)₂]⁺ cation, two non-coordinating water molecules, 0.5 free azide and chloride anions. The disordered azide and chloride anions have a site occupancy of 0.5, respectively. The [Co(2,2-bipy)₂(N₃)₂]⁺ cations are connected to form a ribbon one-dimensional supramolecular structure through intermolecular C—H…π and π…π interactions. Two free water molecules and their crystallographically equivalent H₂O molecules are connected each other to form a cyclic water tetramer by strong intermolecular hydrogen bonds, and then, a [(H₂O)₄(N₃)Cl]^2- anion-water cluster is obtained by the strong intermolecular hydrogen bonds between free water molecules and disordered N^-₃ or Cl^- ions. The quantum calculation of complex [Co(2,2-bipy)₂(N₃)₂]⁺ has been performed by density functional theory method. The single point energy and atomic charge were analyzed, and the oxidation state of the central metal ion was calculated. The results of the calculation are consistent with the experiments.

Synthesis, CT-DNA Binding, and Cytotoxic Activity of Copper(Ⅱ) Complex {[Cu(OMBA)₂]₂·(DMF)₂}

ZENG Zhenfang, CAI Jiehui, HUANG Qiuping, WEI Youhuan, CHEN Limiao, HUANG Qiuchan

2021, 50(12):  2300-2306. 

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In this paper, a copper(Ⅱ) complex {[Cu(OMBA)₂]₂·(DMF)₂} (OMBA=o-methylbenzoic acid, DMF = N,N-dimethylformamide) was synthesized. The structure of the complex was characterized using elemental analysis, infrared (IR) and X-ray single crystal diffraction. The complex belongs to triclinic, P1 space group, with a=1.037 0(5) nm, b=1.053 6(4) nm, c=1.105 9(5) nm, α=62.737(6)°, β=73.355(7)°, γ=63.231(7)°, Z=1, D_c=1.416 g·cm^-3, F(000)=422 unit cell parameters. The final R₁=0.051 5, wR₂=0.140 4. The interaction between CT-DNA (calf thymus DNA) and the complex was evaluated by UV-Vis, fluorescence spectroscopy, and viscometry. When the complex bound to CT-DNA, the binding constant K_b=939.61 L·mol^-1, K_sv=3.00×10³ L·mol^-1, and K_q=3.00×10¹¹ L·mol^-1·s^-1. The complex quenched the intrinsic fluorescence of CT-DNA via static quenching, K_a=5.38×10³ L·mol^-1, n=1. The complex has anti-proliferation effects on A549, Hela and HepG2.

Synthesis of Ag-Chitosan by Green Route and Its Isotherms, Kinetic and Antimicrobial Activity

WANG Zuhua, LIU Ping, YANG Ruixian, CHEN Huajun

2021, 50(12):  2307-2315. 

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A green route, namely adsorption methods, has been developed to synthesize silver-loaded chitosan(Ag-chitosan). The microstructure and thermal stability were studied by X-ray diffraction (XRD), field emission scanning electric mirror (FESEM) and thermal weight analysis. The adsorption model of chitosan on silver was also studied. The antibacterial effect of Ag-chitosan was evaluated by plate diffusion board method. The results show that the introduction of silver ions in the polysaccharide structure affects its original crystal structure and improves its thermal stability. The adsorption isotherm of chitosan to silver ions is consistent with the Langmuir and Dubinin-Radushkevich equations, indicating that the adsorption process of silver ions in chitosan complies with single layer adsorption and chemical adsorption, and the maximum adsorption of chitosan to silver ions is 478.09 mg/g, silver content is 32.34%, which is consistent with the Dubinin-Radushkevich calculation. Therefore, chitosan with 32.34% silver content was obtained and tested against Escherichia coli and Staphylococcus aureus, which is considered one of the most widespread wound burn infectious bacteria. The antibacterial test results indicate that Ag-chitosan has favourable antibacterial property and MIC≤80 μg/mL against Escherichia coli and Staphylococcus aureus.

Influence of Cu(NO₃)₂ in H₂SO₄-H₂O on the Growth of Desulfurized Gypsum Whiskers

WANG Xiao, MA Xiaoxiao, JIN Biao, ZHANG Xiaoting, ZHANG Jianwu, YANG Liushuan, WANG Yubin

2021, 50(12):  2316-2322. 

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Desulfurized gypsum whiskers were prepared by hydrothermal method using treated desulfurized gypsum as raw materials, and Cu(NO₃)₂ was used as the crystal form control agent in the H₂SO₄-H₂O system. The influence mechanism of Cu(NO₃)₂ on the growth of desulfurized gypsum whiskers was discussed. The results show that Cu(NO₃)₂ has obvious dissolution-promoting effect on desulfurized gypsum, and Cu²⁺ could reduce the activity coefficient of each ion in the solution and increase the concentration of Ca²⁺ in the solution. Moreover, NO^-₃ accumulate around Ca²⁺ and shield SO^2-₄ through electrostatic action, which cause the desulfurized gypsum dissolve continuously and keep the concentration of Ca²⁺ and SO^2-₄ in a relatively stable state, and facilitate the nucleation and growth of hemihydrate desulfurized gypsum crystals. In addition, Cu²⁺ selectively adsorb on the surface of the whiskers to generate CuSO₄ during the growth of the whiskers, thereby improve the crystal growth of desulfurized gypsum whiskers. When the amount of Cu(NO₃)₂ is 2.0% (mass fraction), desulfurized gypsum whiskers with an aspect ratio of about 73 are prepared.

Preparation of Resveratrol Nano-Delivery System Based on Mesoporous Silica

ZHANG Wenjun, LI Xiang, ZHANG Guofeng, WANG Qing, LYU Chunyan, LIU Yang

2021, 50(12):  2323-2331. 

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The purpose of this experiment was to construct a mesoporous silicon-encapsulated resveratrol nano-delivery system. The nanosystem before and after loading resveratrol was characterized and analyzed by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N₂ adsorption-desorption, differential thermal-thermogravimetric analysis. Its light and heat stability properties and release laws in different pH buffers in vitro were explored. The results show that the mesoporous silica-encapsulated resveratrol nano-delivery system has a cross-linked network structure. The pore size, specific surface area and pore volume are 10.16 nm, 245.73 m²/g and 0.79 cm³/g, respectively, and the loading capacity could reach 39.44%. The framework structure is not destroyed after loading, and the optical and thermal stability of resveratrol is effectively improved. Meanwhile, the release rate of resveratrol after nanosystem loading is more than 80% within 2 h in two different pH buffers. The mesoporous silica-encapsulated resveratrol nanosystem has better performance and provides reference significance for the further development and utilization of resveratrol.

Preparation and Characterization of NiCo₂S₄@NiCo₂O₄ Composite Electrode with 3D Network Structure

QI Jiabin, QIU Feilong

2021, 50(12):  2332-2338. 

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Supercapacitors with outstanding power density, excellent cycle stability, extremely fast rate performance and environmental friendliness have been widely studied. The performance of supercapacitors is highly dependent on the electrode materials. In this study, Ni-Co-S system was selected and composited as electrode material. Firstly, the NiCo₂O₄ electrode was prepared by hydrothermal method, and it was then transformed into NiCo₂S₄ electrode by ion exchanging method. Then, with chemical bath deposition (CBD) method, the NiCo₂S₄@NiCo₂O₄ composite electrode with 3D network structure was obtained. Further electrochemical studies (CV/Charge-Discharge curves) and SEM images confirm the better specific capacitance and cycle stability of NiCo₂S₄@NiCo₂O₄ composite electrode than that of the single component NiCo₂O₄ electrode, showing great application prospect.

Theoretical Analysis of 4d Metal Doping to Enhance the Optical Sensing Properties of SnO₂ to Acetone

FU Yue, FENG Qing, MOU Zhiyao, GAO Xin, ZHU Hongqiang

2021, 50(12):  2339-2346. 

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Early diabetic patients can be screened out by detecting trace amounts of acetone in human exhaled breath. Therefore, it is a research hotspot to find materials that can detect trace amounts of acetone gas. This paper calculates rutile SnO₂(110) surface charge population (redox performance), density of states, optical properties and adsorption stability after adsorbing acetone molecules, which doped by 4d metal impurities Mo, Ru, Rh, Ag. The effect of 4d metal impurity on optical gas sensing properties was discussed. The results show that: each impurity has varying degrees of influence on the surface redox performance; 4d electrons form impurity peaks near Fermi level. The impurity peak introduced by Ru-4d electrons is the largest, which closest to Fermi level, and the band gap improvement is the greatest; compared to Mo, Rh, and Ag impurity, Ru impurity has the best optical properties in the visible light range (400~760 nm); acetone molecules can be adsorbed on all doped surfaces spontaneously, and the stability order is: Ru>Rh>Ag>Mo. The conclusion shows that Ru-doped SnO₂ is a more effective optical gas detection material for acetone, which is expected to improve the efficiency of early detection and diagnosis of diabetes by detecting acetone in human exhaled breath.

Influences of Alumimum Source Types on Preparation of Ultrafine ZnAl₂O₄ Powders by Molten Salt Method

HUANG Depeng, XU Huan, LIU Jiangbo, FU Yingwen, ZHOU Zhenpeng

2021, 50(12):  2347-2353. 

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In this paper, ZnAl₂O₄ powders were synthesized by molten salt method at 800~1 200 ℃ for 3 h in the mixed molten salt medium of KCl and LiCl using Al(OH)₃, calcined Al₂O₃ and nano-Al₂O₃ as different aluminum sources respectively. The effects of aluminum source types on the synthesis temperature, phase composition and microstructure of the synthesized products were mainly analyzed by XRD, SEM, laser particle size analysis, and specific surface analysis. On this basis, the effects of reaction temperature and the mass ratio of molten salt to raw material (W_s/W_r) on the synthesis of ZnAl₂O₄ powders were discussed. The results show that the type of aluminum source significantly affect the formation temperature of ZnAl₂O₄ and powder performances. Compared with calcined Al₂O₃, the speed of ZnAl₂O₄ formation is faster with Al(OH)₃ and nano-Al₂O₃ as the aluminum sources, and the pure phase ZnAl₂O₄ can be synthesized at 900 ℃. When calcined Al₂O₃ is used as an aluminum source, and the W_s/W_r ratio is 3∶1, the as-synthesized ZnAl₂O₄ powder exhibits best dispersibility, but higher temperatures easily lead to the agglomeration of powders. The formation of ZnAl₂O₄ can be promoted by the appropriate W_s/W_r ratio, and the particle size is the smallest when the W_s/W_r ratio is 4∶1. The ZnAl₂O₄ still retains the initial size and morphology of original Al₂O₃ raw material, indicating that the synthesis of ZnAl₂O₄ by molten salt method is mainly followed the “template synthesis mechanism”.

Composition Optimization of Polishing Slurry for C-Plane Sapphire

JI Jian, LIANG Zhiqiang, ZHOU Hai, JIANG Wang, REN Xiangpu

2021, 50(12):  2354-2361. 

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In this paper, single factor and orthogonal experiments were used to explore the influence of abrasive grain types, polishing slurry pH value, surfactant type, and abrasive grain size on the removal rate of C-plane sapphire chemical mechanical polishing materials. The test results show that: a higher material removal rate and a better surface morphology can obtained when using silica as abrasive particles; the material removal rate shows a trend of first increasing and then decreasing with the increase of the pH value of the polishing slurry, and the pH value of the 9 attachment can get a better removal rate; the material removal rate also increases with the increase of abrasive particle size; using triethanolamine (TEA) and cetyltrimethylammonium bromide (CTAB) as surfactants can get a higher material removal rate; the primary and secondary order of each test factor on the removal rate of sapphire wafer material is abrasive particle size, surfactant, polishing slurry pH value; when the abrasive particle size is 50 nm, the surfactant is CTAB, and the polishing slurry pH value is 9 can get higher material removal rate and better surface quality.

Reviews

Research Progress on Growth Techniques of Single Crystal Fiber

GU Peng, WANG Penggang, GUAN Weiming, ZHENG Li, TAN Yunqiang

2021, 50(12):  2362-2378. 

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Single crystal fibers are widely used in high-power lasers, radiation detection, high-temperature environment monitoring and other fields due to their unique structural characteristics and excellent physical properties. The growth techniques of single crystal fiber are summarized in this article, and further the growth characteristics of techniques, including micro-pulling-down (μ-PD) method, laser heated pedestal growth (LHPG) and edge-defined film-fed growth (EFG) are discussed, the existing issues and solutions in the growth process of single crystal fiber are presented. In addition, the development status and limitations of the cladding preparation techniques are introduced in detail. Finally, the main classification and application scenarios of single crystal fiber at the present stage are expounded and future development is prospected.

Research Progress of MAX Phase Ceramic Materials Based on New Elements and New Multilayer Structures

LI Dandan, HU Qianku, ZHANG Bin, WANG Libo, ZHOU Aiguo

2021, 50(12):  2379-2388. 

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Due to its unique layered structure and special chemical bonding between atoms, MAX phase ceramic materials (chemical formula M_n+1AX_n) have excellent properties of both metal and ceramic materials. These excellent properties make them a promising material in many fields. Since its discovery in the 1960s, it has been paid more attentions. More than 100 MAX phases have been discovered, including more than 80 single phases and a series of solid solutions. The traditional MAX phases are limited to a certain range of elements and the structure in which M₆X layers and single A atomic layer are alternately stacked. The recent successful syntheses of MAX phases containing Au, Ir, Cu, Zn and other elements have largely enriched the MAX phase family. The discovery of multiple A layers and multiple MA layers MAX phases have also opened a door for new MAX phases. With the developments and applications of first-principles calculations and the progresses of modern experimental techniques, more and more new MAX phases have been predicted theoretically or synthesized experimentally. The recent advances on the experimental syntheses and theoretical researches of MAX phases based on new elements and new multilayer structures were summarized, and the problems that need to be overcome in the following researches were pointed out in this article. Finally in order to provide a useful reference for the future, the research directions and developing trends of the new MAX phases are prospected.

Preparation, Functional Modification of Biochar and Its Removal Performance for Organic Pollutants in Wastewater: a Brief Review

ZHOU Yu, CHEN Xiaojuan, LU Kaihong, CHEN Jieming, LI Ning, ZHANG Xinghua

2021, 50(12):  2389-2400. 

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Biochar shows a good application prospect in the field of organic pollution wastewater treatment due to such advantages of wide source of raw materials, large specific surface area, rich pore structure and easy regulation of surface functional groups and so on. However, the different raw materials, preparation methods and modification methods of biochar influence the physical and chemical properties of biochar to a large extent, thus showing different properties and action mechanisms for organic pollution wastewater treatment. Based on the structural characteristics of biochar, the preparation technology, modification methods, as well as the present situation and future development opportunities of biochar for organic pollution wastewater treatment are discussed in this paper.