Reservoir Pore Structure Classification Technology of Carbonate Rock Based on NMR T 2 Spectrum Decomposition

The carbonate reservoir has a number of properties such as multi-type pore space, strong heterogeneity, and complex pore structure, which make the classification of reservoir pore structure extremely difficult. According to nuclear magnetic resonance (NMR) T ₂ spectrum characteristics of carbonate rock, an automatic pore structure classification and discrimination method based on the T ₂ spectrum decomposition is proposed. The objective function is constructed based on the multi-variate Gaussian distribution properties of the NMR T ₂ spectrum. The particle swarm optimization algorithm was used to solve the objective function and get the initial values and then the generalized reduced gradient algorithm was proposed for solving the objective function, which ensured the stability and convergence of the solution. Based on the featured parameters of the Gaussian function such as normalized weights, spectrum peaks and standard deviations, the combinatory spectrum parameters (by multiplying peak value and normalized weight for every peak) are constructed. According to the principle of fuzzy clustering, the carbonate rock pore structure is classified automatically and the discrimination function of each pore structure type is obtained using Fisher discrimination analysis. The classification results were analyzed with the corresponding casting thin section and scanning electron microscopy. The study shows that the type of the pore structure based on the NMR T ₂ spectrum decomposition is strongly consistent with other methods, which provides a good basis for the quantitative characterization of the carbonate rock reservoir pore space and lays a foundation of the carbonate rock reservoir classification based on NMR logging.     

Shape Control of VO2 (B) Hierarchical Nanostructures

A green route is designed to gain a clear idea of growth mechanism of complex VO₂ (B) hierarchical microstructures, since this kind of metal oxide has various metastable phases due to their diverse valence states. Three‐dimensional (3D) uniform flower‐like VO₂ (B) hierarchical microstructure has thus been assembled with the interleaving nanoplates, which are about 25 nm in thickness and well‐crystallized in structure with {114} planes as the dominant surfaces. Results of the systemic control experiments revealed that formation of the flower‐like VO₂ (B) results from a fast nucleation‐growth process, where ethylene glycol (EG) not only acts as a green solvent and reductive agent, but also plays a key role in self‐assembly of the resulted VO₂ (B) hierarchical microstructures. Hydroxyl amount on the solvent molecule is crucial in formation and shape control of VO₂ (B) hierarchical microstructures. Result of this work would be helpful to understand the growth mechanism of complex three‐dimensional hierarchical superstructures of different metal oxides, which is very important to material science and inorganic synthetic chemistry.     

Microstructural evolutions of Pr13Fe80B7 alloys during solid HDDR process

Microstructural evolutions of Pr₁₃Fe₈₀B₇ alloys during solid hydrogenation disproportionation desorption recombination (HDDR) process is systematically investigated. The results show that the early-disproportionated products of Pr₁₃Fe₈₀B₇ alloys are mainly characteristic of rod-like morphology, and the rods are PrH₂ while the matrix is Fe. Moreover, all the PrH₂ rods have the same crystallographic orientation, and grow with a definite orientation related to the Fe matrix. However, it is notable that no iron boride phase except for NdH₂ and Fe is found. With the prolonged disproportionation time, the rod-like disproportionated products coarsen, and the Fe₂B come to form. When the disproportionation time is 17 h, the rod-like disproportionation morphology transforms into sphere, and a large amount of Fe₂B is found. Subsequent investigations for the recombination show that the recombination reactions start at the boundaries between PrH₂ rods and Fe matrix, and the rim-like Pr₂Fe₁₄B is formed on the PrH₂ rods. Moreover, the recombined PrFeB powder of the rod-like microstructure has strong magnetic anisotropy.     

一种厚板薄板通用的新型广义协调元

在适用于中厚板的八结点平板弯曲单元基础上，通过引入剪应变与位移的广义协调条件，建立起一种新型广义协调元，不仅保留了原单元适用于中厚板的特点，同时对薄板也给出了较精确的解，是一种厚板和薄板通用的新型广义协调元。     

Efficient adsorption and photocatalytic degradation of Congo red onto hydrothermally synthesized NiS nanoparticles

The influence of the length of the cation alkyl chain on the dispersibility by ultrasonic treatment of TiO₂ nanopowders in hydrophilic imidazolium-based room temperature ionic liquids was studied for the first time by dynamic light scattering and advanced rheology. TiO₂ nanopowders had been synthesized by chemical vapor synthesis (CVS) under varied conditions leading to two different materials. A commercial nanopowder had been used for comparison. Characterizations had been done using transmission electron microscopy, X-ray diffraction, nitrogen adsorption with BET analysis, and FT-IR spectroscopy. Primary particle sizes were about 6 and 8 nm for the CVS-based and 26 nm for the commercial materials. The particle size distribution in the dispersion was strongly influenced by the length of the cation alkyl chain for all the investigated powders with different structural characteristics and concentrations in the dispersion. It was found that an increase of the alkyl chain length was beneficial, leading to a narrowing of the particle size distribution and a decrease of the agglomerate size in dispersion. The smallest average nanoparticle sizes in dispersion were around 30 nm. Additionally, the surface functionality of the nanoparticles, the concentration of the solid material in the liquid, and the period of ultrasonic treatment control the dispersion quality, especially in the case of the ionic liquids with the shorter alkyl chain. The influence of the nanopowders characteristics on their dispersibility decreases considerably with increasing cation alkyl chain length. The results indicate that ionic liquids with adapted structure are candidates as absorber media for nanoparticles synthesized in gas phase processes to obtain liquid dispersions directly without redispergation.     

Fabrication of nano-network gold films via anodization of gold electrode and their application in SERS

We report here a green and facile one-step method to fabricate nano-network gold films of low roughness via anodization of gold electrodes in an aqueous solution of l-ascorbic acid (AA) or hydroquinone (H₂Q) at the oxidation peak potential. The preparation involves the formation of thin gold oxide layer by anodization of gold and its simultaneous and/or subsequent reduction by AA or H₂Q. The as-fabricated nano-network gold films show very strong SERS activity in comparison with the substrates prepared by some other electrochemical roughening methods.     

Phase composition, microstructures and magnetic properties of melt-spun Nd1.2Fe10.5Mo1.5 ribbons and their nitrides

The effect of wheel speed on the phase compositions and microstructures of melt-spun Nd_1.2Fe_10.5Mo_1.5 ribbon was investigated. It is found that the Nd(Fe,Mo)₁₂ phase can be obtained at the wheel speed of 10 m/s, and TbCu₇-type Nd(Fe,Mo)₇ phase is formed with the wheel speed higher than 10 m/s. The amorphous phase is achieved at 65 m/s. The average grain size of phases decreases linearly with increasing wheel speed. The Nd(Fe,Mo)₁₂N_1.0 nitride obtained from annealed ribbons quenched at 65 m/s shows a coercivity much higher than that from the ribbons quenched at 10 m/s, which is due to the smaller grain size in the former ribbons.     

Magnetocaloric effect in R2Fe17 (R=Sm,Gd, Tb,Dy, Er)

A series of R₂Fe₁₇ (R=Sm, Gd, Tb, Dy, Er) have been synthesized. The magnetocaloric effect (MCE) of these compounds has been investigated by means of magnetic measurements in the vicinity of their Curie temperature. The Curie temperature of Er₂Fe₁₇ is 294 K. The maximum magnetic entropy change of Er₂Fe₁₇ under 5 T magnetic field is ∼3.68 J/kg K. In the R₂Fe₁₇ (R=Sm, Gd, Tb, Dy, Er) system, the maximum magnetic entropy change under 1.5 T magnetic field is 1.72, 0.89, 1.32, 1.59, 1.68 J/kg K corresponding to their Curie temperature (400, 472, 415, 364, 294 K), respectively.     

Effects of the conventional HDDR process and the additions of Co and Zr on anisotropy of HDDR Pr-Fe-B-type magnetic materials

Effects of the conventional hydrogenation disproportionation desorption recombination (HDDR) process and the additions of Co and Zr on anisotropy of HDDR PrFeB-type magnetic materials are investigated. The results show that the degree of anisotropy in conventional HDDR Pr₁₃Fe₈₀B₇ materials decreases monotonically with the prolonged disproportionation time, and short disproportionation time is helpful for preparing highly anisotropic Pr₁₃Fe₈₀B₇ material. However, it is notable that the degree of anisotropy in conventional HDDR Pr₁₃Fe₈₀B₇ materials is significantly smaller than that in solid-HDDR Pr₁₃Fe₈₀B₇ materials with the same disproportionation time. At the same time, it is found that the addition of Co and Zr may make HDDR Pr-Fe-B materials that have higher anisotropy compared with HDDR pure ternary Pr₁₃Fe₈₀B₇ materials under the same HDDR process, but their degree of anisotropy will also decrease monotonically with the prolonged disproportionation time, and will be close to zero when the disproportionation time is greater than 20 h. Based on this, the origin of anisotropy is discussed by X-ray diffraction (XRD) investigations for the disproportionated products of the above alloys. The results show that the origin of anisotropy in HDDR Pr-Fe-B materials with the addition of Co or Zr may differ from that in HDDR pure Pr₁₃Fe₈₀B₇ materials, and the former maybe from the residual “Pr₂(Fe,Co,Zr)₁₄B” nucleus while the latter is not. Finally, it is also found that HDDR Pr-Fe-B materials with Co or Zr can obtain high-magnetic properties even if the high-desorption temperature is used, and this shows the addition of Co and Zr may make HDDR Pr-Fe-B materials that have a larger process temperature range.     

Magnetic domain structures of 1:12 type nitrides NdFe10.5Mo1.5N x

The magnetic domain structures of the 1:12 type alloy NdFe_10.5Mo_1.5 and its nitride were firstly investigated by using magnetic force microscope (MFM). A complicated corrugation and spike magnetic domain structure was observed in NdFe_10.5Mo_1.5alloy. Upon nitrogenation, a stripe domain structure occurs due to the dramatic increase of the uniaxial magneto-crystalline anisotropy K₁ induced by nitrogenation. Based on the basic domain theories, the origin of these domain patterns was analyzed and the reason of domain structure transition is explained quantitatively. The domain wall energy γ, exchange constant A and single-domain particle size D_c of NdFe_10.5 Mo_1.5 and NdFe_10.5-Mo_1.5N _x were calculated in combination with the measured domain width ω and magnetic parameters. A comparison of magnetic parameters with those of SmCo₅ and Nd₂Fe₁₄B permanent materials was also made.