JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS
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2017
·Vol. 55
·期 18
·1373-1379
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IF 2.838
Jiao Chen,Ye Sha,Siyang Gao,Chao Teng,Xiaoliang Wang,Dongshan Zhou,Linling Li,Wei Chen,Gi Xue
Understanding the conformational changes of polymeric chains in solutions is an essential and integral part of polymer physics. By increasing the concentration of polymer solutions from dilute to semidilute regime, the critical chain overlapping has been reported at the concentration termed as C *. In this study, the associated inter- and intrachain conformational transitions in polystyrene (PS) solutions are reported. By comparing the spectroscopic intensity ratio versus concentration for an intrachain PS system, a break point was observed in good solvent which coincided with the theoretically predicted C *. Moreover, the intrachain conformation showed no obvious change below C *, while significant collapse started to occur above C *. This result reveals a new insight in polymer physics, since traditionally the size of polymer chains is considered to decrease weakly regarding the concentration change in the semidilute regime. It is important to find such an abrupt intrachain conformational transition between the dilute and semidilute solutions and provide the first experimental observation that inter- and intrachain conformational transitions are correlated to one the other. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1373–1379
研究领域:
聚合物物理
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材料科学
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产品关联
DOI
高影响因子
DYES AND PIGMENTS
·
2017
·
IF 3.473
Yunjian Wang,Wanying Wu,Xianliang Fu,Mingzhu Liu,Jing Cao,Congying Shao,Shifu Chen
This work explores the phase transition and its impact on photoluminescent properties of metastable scheelite-type, with and without Eu 3+ doped, CdWO 4 nanophosphors. A series of scheelite structure CdWO 4 :xEu 3+ (x = 0, 0.025, 0.05, 0.075, 0.10) samples were synthesized using a simple solvothermal method. The X-ray diffraction results indicate that the prepared samples were single phase in a tetragonal scheelite-type structure, and completely transformed into pure monoclinic wolframite structure after sintering at 450 °C for 2 h. It was revealed by Rietveld analysis that Eu 3+ doping induced a lattice contraction of both scheelite and wolframite CdWO 4 structures. The impact of Eu 3+ doping on the crystal structure and the band structure were further probed by FT-IR, Raman and UV–Vis spectroscopy. SEM images show that the morphology of the prepared samples also changed in the phase transition and the Eu 3+ doping processes. All samples showed a broad multi-color luminescence emission in the range from 400 to 640 nm under 280 nm excitation. The relative intensities of the blue-green emission originated from CdWO 4 matrix and the red emission ascribed to Eu 3+ can be regulated by both the crystal structure and Eu 3+ doping levels. The energy transfer process between WO 4 groups in scheelite structure CdWO 4 and WO 6 groups in wolframite structure CdWO 4 and Eu 3+ was discussed in detail based on the photoluminescent excitation and emission spectra. The synthetic approach reported here allows the control over CdWO 4 polymorphs and this kind of luminescent material has wide applications in white-LED, chemosensors and bioimaging .
研究领域:
材料科学
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光学
✓ 已验证
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DOI
高影响因子
Materials Today Communications
·
2023
·
IF 3.8
Jianhui Su,Yan Liu,Xiujing Peng,Guoxin Sun,Xuchuan Jiang
Due to the high activation energy barrier and the sporadic nature of nucleation, the temperature required for the transition from cubic dense γ-Al 2 O 3 to tripartite α-Al 2 O 3 is as high as 1100–1200 °C. In this work, a two-step strategy was employed to reduce the phase transformation temperature, and prepare α-Al 2 O 3 particles with good dispersion. As the first step, 10 nm sheet γ-Al 2 O 3 was obtained by ammonium aluminum carbonate (AACH) decomposition, which was more favorable to the crystal transformation in the next ball-milling processing. In the second step, γ-Al 2 O 3 powder with partial α-Al 2 O 3 produced in situ by ball-milling γ-Al 2 O 3 was calcined, and α-Al 2 O 3 nanoparticles were obtained at just 850 °C. The content of the α-Al 2 O 3 is determined by the Rietveld Refine method. The relationship between ball-milling time and α-Al 2 O 3 content was clarified, and the effect of α-Al 2 O 3 content on the transformation temperature and morphology of γ-Al 2 O 3 was discussed. The results showed that the α-Al 2 O 3 content rises with the increase of ball milling time, and spherical α-Al 2 O 3 nanoparticles can be obtained when the α-Al 2 O 3 content is 5 %. The addition of α-Al 2 O 3 seeds reduces the phase transition temperature but agglomeration exists. Our proposed two-step low-temperature calcination strategy is an important method for the preparation of alumina nanoparticles
研究领域:
材料科学
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化学工程
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产品关联
DOI
高影响因子
JOURNAL OF PHYSICS-CONDENSED MATTER
·
2025
·Vol. 37
·期 15
·155701
·
IF 2.6
Zekun Yu,Chao Zhou,Kuo Bao,Zhaoqing Wang,Pinwen Zhu,Qiang Tao,Tian Cui
The interactions between the carbon skeleton and metal atoms in binary transition metal carbides are of particular interest for industrial applications involving advanced physics and chemistry, especially in magnetoelectric functional materials and cemented carbides. Cr and carbon BTMCs are a series of intermetallic compounds with specific chemical formulas that share certain unique characteristics. In this study, we used polycrystalline powders of chromium and carbon as precursors and synthesised single-phase bulk Cr7C3 (orthorhombic, space group: Pnma) with high density and good crystallinity using a high-temperature and high-pressure quenching method (HTHPQM). We studied the material properties and electronic structures of Cr7C3 with both experimental measurements and density functional theory ab intio simulations and found that Cr7C3 is a conductor with an electrical conductivity (2.32 × 10−3 Ω m), relatively high compaction (97.2%), excellent thermostability (oxidation at 1175 K), and a magnetic phase transition from paramagnetism to soft ferromagnetism around 50 K, and the electromagnetic properties are chiefly due to the abundance of the 3d electrons of Cr, and the orbital hybridisation between C and Cr with their 2p and 3d electrons is the reason for the crystal structure and high thermostability. Therefore, the synthesised Cr7C3 is a multifunctional material with promising application prospects, and HPHTQM is a simple and effective method for preparing samples.
研究领域:
材料科学
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物理化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
·
2024
·
IF 6.9
Yun Li,Yu Liu,Liyuan Chai,Xin Wang,Dezhou Zhang,Yongming Chen,Yunyan Wang,Shenghai Yang,Yong Ke,Cong Peng,Pingsheng Zeng,Xingwu Lu,Xiaobo Min
PbSO 4 is the main component of lead paste, lead smoke and other lead-containing solid wastes. It usually matches with the primary lead concentrate to co-smelt for lead extraction, mostly in the oxidation smelting stage. The lead waste quickly experiences different temperature and atmosphere fields from feeding the furnace to the completion of the reactions. This work investigated PbSO 4 decomposition kinetic and phase transformation mechanism during lead waste pyrometallurgical recycling. The results show that the activation energy of the decomposition reaction of PbSO 4 at 800 ℃∼1000 ℃ in Ar atmosphere is 121.35 kJ/mol. The PbSO 4 decomposition reaction in Ar and Air is a multi-step decomposition process, which may undergo PbSO 4 → PbO·PbSO 4 → 2PbO·PbSO 4 → 4PbO·PbSO 4 → PbO. PbO is not generated through direct decomposition of PbSO 4 . The results are expected to provide guidance for the lead wastes co-smelting process to achieve a target PbSO 4 decomposition product.
研究领域:
冶金学
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材料科学
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产品关联
DOI
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
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2022
·
IF 14.224
Jing Zhang,Wenyu Xie,Shasha Chu,Zhangbin Liu,Zhen Wu,Yingying Lan,Vladimir V. Galvita,Lijuan Zhang,Xintai Su
Chromium ore processing residue (COPR) is a hazardous waste generated during the production of chromate. Currently, approximately 10% of Cr 2 O 3 cannot be extracted after chromite sodium roasting and remains in COPR, wasting valuable Cr resources. In this study, Mg was selectively removed by using (NH 4 ) 2 SO 4 roasting in combination with H 2 SO 4 leaching. The results showed that the selective removal of 79.55% Mg from COPR could be achieved under the optimum (NH 4 ) 2 SO 4 roasting conditions (80 mmol (NH 4 ) 2 SO 4 , 800 °C, 2 h). During the subsequent sodium roasting and acid leaching stages, the Cr extraction rate was 84.63% for the COPR direct roasting and 95.39% for the Mg removal residue roasting. The increased Cr extraction efficiency is attributed to the transformation of Mg-rich spinel and diopside (the Mg & Cr coexisting phases) in COPR converted into easily extractable (Fe,Cr) 2 O 3 and Cr 2 O 3 after the Mg treatment. This study investigated that the phase transformation of the Cr host phases is crucial for the sufficient extraction of Cr and provides inspiration for the development of efficient and practical Cr extraction techniques. Moreover, the method can be extended to the effective extraction of Cr from other Cr-containing wastes.
研究领域:
冶金工程
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环境科学
✓ 已验证
DOI
PubMed
高影响因子
Soft Matter
·
2011
·Vol. 7
·期 16
·7526-7531
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IF 4.457
Shengtong Sun,Peiyi Wu
Highly branched poly(N-isopropylacrylamide) (PNIPAM) was first synthesized by self-condensing atom transfer radical copolymerization (SCATRCP) catalyzed by CuBr/tris[2-(dimethylamino)ethyl]amine (Me6TREN) complex in isopropanol at room temperature. This method showed good control over chain morphology and lower critical solution temperature (LCST) type phase transition behavior of PNIPAM by varying reaction time and monomer/inimer feed ratios. On the basis of GPC, FTIR, 1HNMR and DSC results, four stages were discerned during the polymerization procedure, at which chain architectures experienced “linear – comblike – slightly branched – highly branched” transformations. Additionally, the synthesized highly branched PNIPAM chains were found to be able to self-assemble into hollow spheres in alcohols such as methanol and ethanol, which arise from the presence of large amounts of hydrophobic branched points inside polymer chains.
研究领域:
高分子化学
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材料科学
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物理化学
✓ 已验证
产品关联
DOI
高影响因子
CRYSTAL GROWTH & DESIGN
·
2021
·
IF 4.076
Mengnan Li,Chengyu Gong,Guobin Ren,Xiaoyong Xu,Minghuang Hong,Zhong Li
Although plant virus disease is destructive for economic losses of agricultural production, few studies focus on the field of solid state of pesticides. Dufulin (DFL) is a novel plant antiviral agent with high efficiency but low solubility and is easy to agglomerate during the process of crystallization. In this paper, the polymorphism behavior of DFL was systematically studied. Five polymorphs (Forms I–IV and VI), a solvate (Form V) and an amorphous form were discovered and characterized by powder X-ray diffraction and thermal analytical methods. Single crystals of Forms I, III, IV, V, and VI were obtained and their structures were identified by single-crystal X-ray diffraction. Based on the results of stability experiments (solid-state stability and solvent-mediated transition), thermal analysis methods, solubility studies and powder dissolution experiments, Form I appeared to be the thermodynamically most stable phase with the lowest solubility under ambient conditions, closely followed by Form III. In addition, the relative stability of the different crystal forms was simulated by density functional theory. As the result, the thermodynamic order of different forms was as follows: I > III > II > IV > VI > V. It is the first time that seven crystalline forms of DFL are reported, which fills the blank of DFL in the crystal engineering field and prompts the development of the formulation.
研究领域:
农药学
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晶体工程
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药物化学
✓ 已验证
DOI
高影响因子
Polymer Chemistry
·
2014
·Vol. 5
·期 13
·4105-4114
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IF 5.368
Xi Chen,Nan Zheng,Qiao Wang,Lingzhi Liu,Yongfeng Men
The influence of different synthetic pathways on the phase transition and side-chain crystallization behavior of cellulose ethers was systematically investigated by a combination of differential scanning calorimetry (DSC), small and wide-angle X-ray scattering (SAXS, WAXS) and Fourier transform infrared spectroscopy (FTIR) techniques. DSC investigation indicated that the melting temperature and crystallization temperature, respectively, of cellulose derivatives that were synthesized by homogeneous reactions in cellulose solutions differed from those of cellulose aggregates in a swollen state synthesized by heterogeneous reactions; this implies that the synthetic pathway had a strong effect on the side-chain crystallization behavior in comb-like polymers. WAXS results showed that the cellulose ethers prepared by homogeneous reaction packed into hexagonal crystals, while those prepared by heterogeneous reaction exhibited multiple crystals. These phenomena may be understood as a result of the effect of the regularity of the main chain and the difference in hydrogen bonding interactions in the two kinds of cellulose ethers. For the latter, the presence of free –OH groups at the C-6 position in the samples obtained via the heterogeneous reaction is considered to contribute critically to intermolecular hydrogen bonds that promote crystallization of the system.
研究领域:
材料科学
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聚合物化学
✓ 已验证
DOI
高影响因子
NANOTECHNOLOGY
·
2024
·Vol. 35
·期 15
·155401
·
IF 2.9
Hongjing Wang,Tongqing Zhou,Shan Xu,Kai Deng,Hongjie Yu,You Xu,Xiaonian Li,Ziqiang Wang,Liang Wang
The development of effective and stable cathode electrocatalysts is highly desired for fuel cells. Controlling the composition and morphology of Pd-based materials can provide a great opportunity to improve their oxygen reduction reaction (ORR) performance. Here, we report the synthesis of hexagonal close-packed (hcp) Pd2B nanosheet assemblies (Pd2B NAs) via the boronation reaction between as-synthesized Pd NAs and N,N-dimethylformamide. The hcp Pd2B NAs with uniform pore distribution can provide sufficient active sites for ORRs. The insertion of B atoms can induce the phase transition from face-centered cubic structure to hcp structure, as the most thermodynamically stable phase in the Pd-B alloy, which is beneficial for enhancing the ORR stability and toxicity resistance. Therefore, the hcp Pd2B NAs exhibit superior mass activity, specific activity and excellent stability for ORR. The present strategy of boron-intercalation-triggered crystalline transition of Pd-based nanomaterials is valuable for the design of metal–nonmetal catalysts with enhanced performance.
研究领域:
材料科学
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电化学
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催化科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE
·
2023
·Vol. 54
·期 2
·969-979
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IF 3
Cao Shuheng,Liu Zhihong,Lu Xingwu,Zhang Leru,Li Qihou,Xia Longgong
Copper smelting slag is the largest solid waste produced in copper-making process, and slow cooling beneficiation technology is the most widely used method in recovering remaining treasures from the slag. The phase transition law and element distribution behaviors of the copper smelting slag in the cooling process have significant importance, and they have been experimentally investigated in the present study. CaS, which was produced from the reductive decomposition of gypsum residue, has been added for sulfidation purposes to improve the recovery. Fayalite, glassy slag, hercynite, magnetite, and matte were major phases in the final slag, and the adding amount of CaS had a small effect on the phase transition process. However, the cooling rate had a large effect on the slag phase composition. When decreasing the cooling rate, the mass fraction of glassy slag decreased dramatically. The distribution behavior of Fe, Cu, Zn, Pb, Se, Te, and Ag changed when increasing the CaS adding dosage, and that of Si, Ca, Al, and Mg changed slightly. The initial slag composition also influenced the element distribution behavior. When changing the CaS excess coefficient, the distribution behavior of As and Bi changed slightly in the slag with the initial Fe/SiO 2 mass ratio of 1.8. But when the smelting slag had the Fe/SiO 2 mass ratio of 1.0 and 1.3, more As entered the glassy slag when increasing the CaS adding dosage. Less Ca reported to the glassy slag when decreasing the cooling rate, and more Cu, Pb, Zn, Se, Te, and Ag entered the matte phase, but part of them were lost in the cooling process. Graphical Abstract
研究领域:
冶金学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
Food Science and Technology
·
2022
·
IF 2.602
ZHANG Chunlan,NING Yuli,JIA Yin,KANG Mengyao,HE Yawen,XU Wei,SHAH Bakht Ramin
Phase transition of lysozyme/carrageenan (Ly/CRG) complex system with different ratios, pH, ionic strength and temperature conditions was explored through ultraviolet-visible spectrophotometer, fluorescence spectrophotometer, fluorescence microscope, Zeta potential. The results showed that the main force between Ly and CRG is electrostatic interaction, and the Ly/CRG composite system has undergone three phase transition states: co-solubilization, gelation and aggregation. At pH = 1-3, the oppositely charged CRG and Ly form complexes based on electrostatic interaction. Whereas at pH = 12, both CRG and Ly are negatively charged and they repel each other electrostatically. The electrostatic shielding effect of salt ions had a greater impact on the formation of Ly/CRG complex. Temperature had a certain degree of influence on the structure and turbidity of the composite system. The interaction between polysaccharides and proteins can have a significant impact on the structure and stability of complex systems and the study of polysaccharide and protein complexes which will help to expand their application in food and medicine.
研究领域:
食品科学
·
生物化学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）