The structure of poly-m-phenylene isophthalamide gel-state fibre. The mechanism of diffusion precipitation

1976 ◽  
Vol 7 (3) ◽  
pp. 235-239
Author(s):  
E. P. Krasnov ◽  
L. D. Rudneva ◽  
E. A. Vorobev
Keyword(s):  
Diffusion Precipitation

scholarly journals Fabrication of C/C–SiC–ZrB2 Ultra-High Temperature Composites through Liquid–Solid Chemical Reaction

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1352
Author(s):  
Qian Sun ◽  
Huifeng Zhang ◽  
Chuanbing Huang ◽  
Weigang Zhang
Keyword(s):  
High Temperature ◽  
Ceramic Composites ◽  
Dense Matrix ◽  
Ablation Resistance ◽  
The Matrix ◽  
Melt Infiltration ◽  
Reactive Melt Infiltration ◽  
Reactive Melt ◽  
Diffusion Precipitation ◽  
Ultra High Temperature

In this paper, we aimed to improve the oxidation and ablation resistance of carbon fiber-reinforced carbon (CFC) composites at temperatures above 2000 °C. C/C–SiC–ZrB2 ultra-high temperature ceramic composites were fabricated through a complicated liquid–solid reactive process combining slurry infiltration (SI) and reactive melt infiltration (RMI). A liquid Si–Zr10 eutectic alloy was introduced, at 1600 °C, into porous CFC composites containing two kinds of boride particles (B4C and ZrB2, respectively) to form a SiC–ZrB2 matrix. The effects and mechanism of the introduced B4C and ZrB2 particles on the formation reaction and microstructure of the final C/C–SiC–ZrB2 composites were investigated in detail. It was found that the composite obtained from a C/C–B4C preform displayed a porous and loose structure, and the formed SiC–ZrB2 matrix distributed heterogeneously in the composite due to the asynchronous generation of the SiC and ZrB2 ceramics. However, the C/C–SiC–ZrB2 composite, prepared from a C/C–ZrB2 preform, showed a very dense matrix between the fiber bundles, and elongated plate-like ZrB2 ceramics appeared in the matrix, which were derived from the dissolution–diffusion–precipitation mechanism of the ZrB2 clusters. The latter composite exhibited a relatively higher ZrB2 content (9.51%) and bulk density (2.82 g/cm3), along with lower open porosity (3.43%), which endowed this novel composite with good mechanical properties, including pseudo-plastic fracture behavior.

scholarly journals Parasitological and serological studies on amoebiasis and other intestinal parasitic infections in the rural sector around Recife, Northeast Brazil

1990 ◽  
Vol 32 (6) ◽  
pp. 428-435 ◽  
Author(s):  
José Felipe Gonçalves ◽  
Masanobu Tanabe ◽  
Francisco de Paula de Melo Medeiros ◽  
Fernando José Gonçalves ◽  
Ivanize da Silva Aca ◽  
...  
Keyword(s):  
Intestinal Parasites ◽  
Strongyloides Stercoralis ◽  
Common Species ◽  
Test Tube ◽  
Enzyme Linked Immunosorbent Assay ◽  
Parasitic Infections ◽  
Intestinal Parasitic Infections ◽  
High Prevalence ◽  
Serological Studies ◽  
Diffusion Precipitation

Parasitological examinations were carried out during July to December, 1989, on 485 inhabitants of four villages in São Lourenço da Mata, 25 km northwest of Recife, Pernambuco, Brazil. Approximately 99.6% of the inhabitants were infected with at least one species of intestinal parasites. A high prevalence of Schistosoma mansoni (82.1%), hookworm (80.2%) Trichuris trichiura (69.9%), Ascaris lumbricoides (61.9%) and Entamoeba coli (36.7%) infections were demonstrated. Test tube cultivation revealed that the most common species of hookworm in this region was Necator americanus (88.4%), and also that the prevalence of Strongyloides stercoralis was 5.8%. Three hundred and thirty-four sera were serologically examined for amoebiasis by the gel diffusion precipitation test (GDP) and enzyme-linked immunosorbent assay (ELISA). No positive reaction was observed in all sera as examined by GDP, while 24 sera were positive by ELISA.

Discussion of Wetting Phenomena Under Reducing Atmospheres Using a High Resolution Wetting Balancem

1986 ◽  
Vol 72 ◽  
Author(s):  
B. Jahnke ◽  
H. Reiss
Keyword(s):  
High Resolution ◽  
Interfacial Energies ◽  
Wetting Phenomena ◽  
Adsorption Processes ◽  
Metallographic Inspection ◽  
Diffusion Precipitation

AbstractIn wetting phenomena surface and interfacial energies play an important part. Due to diffusion, precipitation and adsorption processes these energies are time and temperature dependently changing. The influence on wetting behaviour is investigated using a high resolution wetting balance and metallographic inspection.

Modelling of diffusion–precipitation in nitrided alloyed iron

2000 ◽  
Vol 377-378 ◽  
pp. 543-549 ◽  
Author(s):  
M. Gouné ◽  
T. Belmonte ◽  
J.M. Fiorani ◽  
S. Chomer ◽  
H. Michel
Keyword(s):  
Alloyed Iron ◽  
Diffusion Precipitation

Strong solvability up to clogging of an effective diffusion–precipitation model in an evolving porous medium

2016 ◽  
Vol 28 (2) ◽  
pp. 179-207 ◽  
Author(s):  
R. SCHULZ ◽  
N. RAY ◽  
F. FRANK ◽  
H. S. MAHATO ◽  
P. KNABNER
Keyword(s):  
Differential Equation ◽  
Ordinary Differential Equation ◽  
Level Set ◽  
Diffusion Tensor ◽  
Effective Diffusion ◽  
Partial Differential ◽  
Linear Diffusion ◽  
Precipitation Model ◽  
Effective Coefficients ◽  
Diffusion Precipitation

In the first part of this article, we extend the formal upscaling of a diffusion–precipitation model through a two-scale asymptotic expansion in a level set framework to three dimensions. We obtain upscaled partial differential equations, more precisely, a non-linear diffusion equation with effective coefficients coupled to a level set equation. As a first step, we consider a parametrization of the underlying pore geometry by a single parameter, e.g. by a generalized “radius” or the porosity. Then, the level set equation transforms to an ordinary differential equation for the parameter. For such an idealized setting, the degeneration of the diffusion tensor with respect to porosity is illustrated with numerical simulations. The second part and main objective of this article is the analytical investigation of the resulting coupled partial differential equation–ordinary differential equation model. In the case of non-degenerating coefficients, local-in-time existence of at least one strong solution is shown by applying Schauder's fixed point theorem. Additionally, non-negativity, uniqueness, and global existence or existence up to possible closure of some pores, i.e. up to the limit of degenerating coefficients, is guaranteed.

scholarly journals Research on the Tensile Properties of Packaging Film Based on Environmental Protection PVA-KGM

2021 ◽  
Author(s):  
Ligui Xiong ◽  
Liqiong Zhang
Keyword(s):  
Tensile Strength ◽  
Environmental Protection ◽  
Tensile Properties ◽  
Vinyl Alcohol ◽  
Poly Vinyl Alcohol ◽  
Homogeneous State ◽  
Elongation At Break ◽  
Packaging Films ◽  
Polyelectrolyte Solution ◽  
Diffusion Precipitation

Konjac glucomannan (KGM) and poly (vinyl alcohol) (PVA) were mixed to form gel-like polyelectrolyte solution with glycerol and sorbitol as compound plasticizer, which was used to prepare packaging films via casting and drying. The results show that the tensile strength and elongation at break of the packaging films drop sharply when the blending temperature and blending time exceed 80 °C and 3.5 h. When the mass ratio of sorbitol and glycerol in the compound plasticizer ranges from 1:1 to 1:3, it is beneficial to improve the tensile strength of the packaging films. The microscopic reasons for the change of the tensile properties of the packaging films are mainly caused by diffusion-stop-continuing diffusion—precipitation of low-molecular electrolyte, which makes the system shift from equilibrium-homogeneous state- unbalanced state—heterogeneous state.

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