Preparation and Characterisation of Polyborazine as Novel Precursor to Boron Nitride Ceramic

2011 ◽  
Vol 194-196 ◽  
pp. 1749-1754
Author(s):  
Cheng Deng ◽  
Yong Cai Song ◽  
Meng Fu Zhu ◽  
Hong Bo Su ◽  
Xiu Dong You ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Melt Spinning ◽  
Condensation Reaction ◽  
Average Molecular Weight ◽  
Nitrogen Atmosphere ◽  
Minor Amount ◽  
Ceramic Fibers ◽  
Ceramic Yield ◽  
Linear Arrangement ◽  
Element Analysis

A processable polyborazine precursor was synthesized via substitution reaction and deamine condensation reaction by using methylamine, propylamine and B-trichloroborazine (TCB) as the starting materials. The chemical composition, structure and properties of the obtained polymer were investigated using element analysis, FT-IR, NMR, XPS and TG. The results indicated that the backbone of the polymer was approximate linear arrangement of boron-nitride ring molecules with B-N(CH3)-B structure as bridge bond, meanwhile minor amount of methylamino and propylamino remained in polyborazine as the pendant or end group. The melting point, number average molecular weight and polydispersity index of polyborazine was 90°С , 1002 and 1.355, respectively. The polyborazine showed good processability and polyborazine precursor fibers with diameter of 10~15 µm could be obtained by melt-spinning in N2 atmosphere. The ceramic yield of the polyborazine at 1000°С in nitrogen atmosphere was 53.2 wt%, which suggested that the as-achieved polymer can be used as a precursor to boron nitride ceramic fibers and membranes.

A New Generation of Boron-Based Ceramic Fibers: Design, Processing and Properties of SilicoBoron CarboNitride (SiBCN) Fibers from Boron-Modified Polyvinylsilazanes

2006 ◽  
Vol 50 ◽  
pp. 9-16 ◽  
Author(s):  
Samuel Bernard ◽  
Markus Weinmann ◽  
David Cornu ◽  
Philippe Miele
Keyword(s):  
Melt Spinning ◽  
Structural Changes ◽  
Fiber Strength ◽  
Xrd Analysis ◽  
Nitrogen Atmosphere ◽  
Ceramic Fibers ◽  
Ceramic Yield ◽  
Flexible Form ◽  
Shaping Process ◽  
Spinning Process

Boron-modified polyvinylsilazanes have been studied for suitability as fiber precursor. A melt-tractable polymer displaying Si- and N-bonded methyl groups was successfully processed into green fibers ~18μm in diameter via a melt-spinning process. After the shaping process, the use of an ammonia curing atmosphere at 200°C allowed to increase the ceramic yield of the polymer, then avoid inter-fiber fusion during the further increase of the temperature. As-cured fibers were annealed in the temperature range 1000-1800°C in a nitrogen atmosphere to provide SiBCN ceramic fibers black colored, of flexible form and ~12μm in diameter in different crystallinity states going from totally amorphous below 1600°C to well-crystallized at 1800°C. The excellent strength retention after heat-treatment at 1600°C (1.3-1.5GPa) is clearly related to the high amorphous stability of fibers. Elemental compositions of such amorphous fibers showed a typical chemical formula of Si3.0B1.0C5.0N2.4. Between 1600°C and 1700°C, the fiber strength decreased to 0.9GPa then dropped to about one-quarter the original value at 1800°C while structural changes were evident by XRD analysis.

Silicon Carbide Base Ceramic Fiber Synthesis from Polycarbosilane-Modified Polymethylsilane Blend Polymers by Melt Spinning

2011 ◽  
Vol 675-677 ◽  
pp. 139-142
Author(s):  
Xin Xing ◽  
Lin Liu ◽  
Feng Cao ◽  
Xiao Dong Li ◽  
Zeng Yong Chu ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Tensile Strength ◽  
Thermal Oxidation ◽  
Melt Spinning ◽  
Ceramic Fiber ◽  
Ceramic Yield ◽  
Base Ceramic

A melt-spinnable precursor for SiC based fibers was prepared from blend polymers of polycarbosilane (PCS) and modified polymethylsilane (M-PMS). The blend polymers cured at 320°C are different from M-PMS and PCS. The ceramic yield of these blend polymers is about 83%. The C/Si ratio of M-PMS/PCS derived ceramics (pyrolyzed at 1250°C) is linear to the content of MPMS in M-PMS/PCS. After melt spinning, thermal oxidation curing, and pyrolysis, Si-C-O fibers were obtained. The diameter and the tensile strength of the resulted fibers are 16.5μm and 1.62GPa, respectively.

Effects of Anti-Oxidants on Size Distribution of Polycaprolactam during Melting and Melt-Spinning

1977 ◽  
Vol 47 (2) ◽  
pp. 132-139 ◽  
Author(s):  
T. K. Bhattacharya ◽  
MD. Abubakkar ◽  
A. K. Mukherjee
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Thermal Degradation ◽  
Size Distribution ◽  
Melt Spinning ◽  
Distribution Curve ◽  
Atmospheric Condition ◽  
Nitrogen Atmosphere ◽  
Atmospheric Conditions

The changes in the size distribution of polycaprolactam that take place during melting and melt-spinning have been studied. During melting under a nitrogen atmosphere, thermal degradation as well as post polymerization takes place. Spinning the polymer under atmospheric conditions, thermal, thermo-oxidative, and mechanical degradations come into play. Post polymerization is also operative in this case. The net change that is being encountered in these processes is a broader size distribution of the polymer as compared to that of the parent one. The effects of three different anti-oxidants, which are paraphenylene diamine derivatives, on the size distribution of polycaprolactam during melting and melt-spinning have been studied. Anti-oxidants are found to check the broadening of the size-distribution curve and retain the mechanical properties of the material to an appreciable extent, even after heat treatment at a temperature of 160°C for 8 hours under atmospheric condition.

scholarly journals Structure, stability, and properties of phenolic fibers modified by phenyl molybdate

2020 ◽  
pp. 096739112092780
Author(s):  
Yang Kai ◽  
Jiao Mingli ◽  
Zhang Xiaomei ◽  
Jia Wanshun ◽  
Diao Quan ◽  
...  
Keyword(s):  
Melt Spinning ◽  
Main Chain ◽  
Phenol Formaldehyde ◽  
Gel Permeation Chromatography ◽  
Decomposition Temperature ◽  
Nitrogen Atmosphere ◽  
Molecular Structures ◽  
Structure Stability ◽  
Initial Decomposition Temperature ◽  
Heat Curing

Phenyl molybdate-modified phenolic fibers (PMoPFs) were prepared by melt spinning from the corresponding resin which was polymerized from phenol, formaldehyde, and phenyl molybdate, followed by solution curing and then heat curing processes. The molecular structures, including characteristic groups and molecular weight, were examined by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. The influences of the curing processes were demonstrated by mechanical properties, scanning electron microscopy, and thermogravimetric analysis characterization. PMoPF with 8 wt% molybdic acid and cured in an oven possessed a tensile strength as high as 187 MPa, initial decomposition temperature of 300°C, and a char yield under nitrogen atmosphere at 800°C as high as 66.0%, with the molybdate (MoO4 2−) groups being introduced into the phenolic main chain.

Facility for Continuous CVD Coating of Ceramic Fibers

1991 ◽  
Vol 250 ◽  
Author(s):  
Arthur W. Moore
Keyword(s):  
Boron Nitride ◽  
High Temperatures ◽  
Weight Ratio ◽  
High Strength ◽  
Ceramic Coatings ◽  
Ceramic Composites ◽  
Ceramic Fiber ◽  
Ceramic Fibers ◽  
Fiber Properties ◽  
Nitride Coatings

The development of new and improved ceramic fibers has spurred the development and application of ceramic composites with improved strength, strength/weight ratio, toughness, and durability at increasingly high temperatures. For many systems, the ceramic fibers can be used without modification because their properties are adequate for the chosen application. However, in order to take maximum advantage of the fiber properties, it is often necessary to coat the ceramic fibers with materials of different composition and properties. Examples include (1) boron nitride coatings on a ceramic fiber, such as Nicalon silicon carbide, to prevent reaction with the ceramic matrix during fabrication and to enhance fiber pullout and increase toughness when the ceramic composite is subjected to stress[l]; (2) boron nitride coatings on ceramic yarns, such as Nicalon for use as thermal insulation panels in an aerodynamic environment, to reduce abrasion of the Nicalon and to inhibit the oxidation of free carbon contained within the Nicalon[2]; and (3) ceramic coatings on carbon yarns and carbon-carbon composites to permit use of these high-strength, high-temperature materials in oxidizing environments at very high temperatures[3,4].

Polycondensation of Urea and Boric Acid to Give Polyborate Ester, a Precursor for Boron Nitride

2007 ◽  
Vol 29-30 ◽  
pp. 199-202 ◽  
Author(s):  
S. Mondal ◽  
A.K. Banthia
Keyword(s):  
Boron Nitride ◽  
Boric Acid ◽  
Elemental Analysis ◽  
High Performance ◽  
Powder Processing ◽  
Condensation Reaction ◽  
Ceramic Materials ◽  
Attractive Alternative ◽  
Condensation Polymerization ◽  
Multifunctional Compounds

Polycondensations (condensation polymerization) are stepwise reactions between bifunctional or polyfunctional compoents, with elimination of simple molecules such as water or alcohol and the formation of macromolecular substances. Polyborate ester , formed by this process, gives ceramic materials during pyrolysis. Polymer pyrolysis offers an attractive alternative to the typical high temperature powder processing approach in the fabrication of high-performance ceramics. This approach might also prove to be useful in the fabrication of fibers, coatings, and composites. It is within this framework that the present study was undertaken; its aim is the preparation of boron-containing oligomeric precursors which gives boron nitride after pyrolysis. The precursor was synthesized by the condensation reaction between boric acid and urea (or other N-containing reactive multifunctional compounds). The oligomeric precursor and its pyrolysed products were thoroughly characterized by elemental analysis, IR, NMR, XRD, Thermal Analysis and Transmission Electron Microscopy(TEM). The elemental analysis results of the oligomer are---- C-13.40%, H-5.97%, N-32.44% and B-17.09%. X-ray diffraction and TEM studies showed that boron nitride obtained from this system possess tetragonal structure.

Evolution of Composition and Structure of Poly[(alkylamino)borazine] to Boron Nitride Ceramic during Pyrolysis Process

2014 ◽  
Vol 602-603 ◽  
pp. 146-150
Author(s):  
Cheng Deng ◽  
Meng Fu Zhu ◽  
Hong Bo Su ◽  
Xiu Dong You ◽  
Ping Chen
Keyword(s):  
Boron Nitride ◽  
Condensation Reaction ◽  
Three Dimensions ◽  
Curing Process ◽  
Pyrolysis Process ◽  
Cross Link ◽  
Thermal Pyrolysis ◽  
Transamination Reaction ◽  
Composition And Structure ◽  
Xrd Techniques

Boron nitride (BN) was prepared by polymer-derived method using precursor poly [(alkylamino) borazin (PABZ). The evolution of composition and structure of precursor PABZ into BN ceramic during curing and pyrolysis process was investigated by FTIR, TG, XRD techniques and chemical analysis. The results showed that PABZ could fulfill curing heated at 80°C for 2hrs in NH3 atmosphere. During the curing process the both transamination reaction and condensation reaction occurred, resulting in cross-link between monomer molecular. With the proceeding of curing process, the new B-N bonds were formed and continued to expand in three dimensions. After cured treatment the thermal pyrolysis of PABZ in ammonia atmosphere was took place, and inorganic degree and crystallinity of products were better, which was more suitable for preparation of high purity hexagonal BN (h-BN) ceramic.

Preparation of SiBCN Microtubes from Melt-Spinnable Polymers

2008 ◽  
Vol 368-372 ◽  
pp. 926-928 ◽  
Author(s):  
Laura Gottardo ◽  
Samuel Bernard ◽  
Marie Paule Berthet ◽  
Philippe Miele
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Nitrogen Atmosphere ◽  
Low Molecular Weight ◽  
Ceramic Fibers ◽  
Preceramic Polymers ◽  
Flexible Form ◽  
First Time

SiBCN microtubes were prepared for the first time by spinning a low molecular weight preceramic polymers of boron-modified polyvinylsilazanes into green fibers ~30 m in diameter which were subsequently thermolyzed under a nitrogen atmosphere. Hollow SiBCN ceramic fibers black colored, of flexible form, ~20 m in diameter and 0.8GPa in tensile strength were produced.

scholarly journals Controlled Release of Benzocaine from Monomer and Copolymer Carriers in Synthetic Gastro-intestinal Media

2014 ◽  
Vol 3 (2) ◽  
pp. 853
Author(s):  
Houaria Merine ◽  
Abderrezzak Mesli ◽  
Nafa Chafi ◽  
Zohra Bengharez
Keyword(s):  
Controlled Release ◽  
Drug Release ◽  
Condensation Reaction ◽  
Average Molecular Weight ◽  
Aqueous Media ◽  
Control Drug ◽  
Elemental Analyses ◽  
Intestinal Fluids ◽  
Fraction I ◽  
Control Drug Release

<p class="Default">New dosage forms able to control drug release in the gastro-intestinal media have been prepared and investigated in this paper. Two different type of medicinal agent bonding (MA), in our case Benzocaine (Bz), were chosen in order to examine drug release.</p><p class="Default">i) MA attached to ethylenic monomer (m,p-vinylbenzaldehyde), condensation reaction.</p><p class="Default">ii) The copolymer carrier (Cp) is obtained by copolymerizing this monomer.</p><p class="Default">These two carriers were well characterized by microanalysis, FTIR, DSC (Tg) and GPC (Ip) and the two fraction α and β were calculated from elemental analyses of Cp. The results showed good polydispersity and low average molecular weight. MA linked to an organic product by the azomethine function (C=N), hydrolytically sensitive, allowed controlled release of Bz, from the monomer carrier and from the bending Schiff bases groups. Theoretical and experimental analyses of controlled release of Bz kinetics from monomer and copolymer carriers were conducted for the case of contact with synthetic gastro-intestinal fluids at various pH (1,2; 6,0 and 8,0) at 37°C.</p><p class="Default">The process was found to be controlled by the nature of media (heterogeneous), which involved the preliminary hydrolysis, and the drug (Bz) diffusing out of structure of copolymer (Cp) to the external aqueous media.</p><p class="Default">The results obtained on the rate of delivery showed a clear difference between pH = 1,2 and pH = 6,0 and 8,0 based on:</p><p class="Default">i) The cation of p-aminoniumbenzoic acid (PABAH+) release at pH = 1,2</p><p class="Default">ii) Bz release at pH = 6,0 and 8,0</p>

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