scholarly journals Effect of HPHT Treatment on Spectroscopic Features of Natural Type Ib-IaA Diamonds Containing Y Centers

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 378 ◽  
Author(s):  
Igor N. Kupriyanov ◽  
Yuri N. Palyanov ◽  
Alexander A. Kalinin ◽  
Vladislav S. Shatsky
Keyword(s):  
Emission Band ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Absorption Feature ◽  
Spectroscopic Techniques ◽  
Annealing Stage ◽  
Natural Diamonds ◽  
Phonon Spectra ◽  
Before And After ◽  
Natural Type

In this paper, we report a spectroscopic study of natural type Ib-IaA diamonds containing Y centers subjected to high-pressure high-temperature treatment at 7–7.5 GPa and 1700–2200 °C. Diamond samples showing the Y centers as the dominant absorption feature in the infrared spectra were selected from a collection of natural diamonds from alluvial placers of the northeastern Siberian Platform. The samples were investigated by spectroscopic techniques before and after each annealing stage. It was found that upon annealing at temperatures higher than 2000°C, the defect-induced one-phonon spectra changed from the Y centers to a new form with a characteristic band peaking at 1060 cm−1. Photoluminescence spectra of the samples were modified after each annealing stage starting from 1700 °C. The most significant changes in photoluminescence occurred at temperatures higher than 2000 °C and were associated with a sharp increase of the intensity of an emission band peaking at about 690 nm. A comparison with natural red-luminescing diamonds from Yakutian kimberlite pipes was performed. It was concluded that the observed 1060 cm−1 IR band and the 690 nm red emission band are genetically related to the Y centers and that defects or impurities responsible for the Y centers appear quite widespread in natural diamonds from various deposits worldwide.

Scanning tunneling microscope study of polyacrylonitrile-based carbon fibers

1997 ◽  
Vol 12 (10) ◽  
pp. 2543-2547 ◽  
Author(s):  
Dongxia Shi ◽  
Ning Liu ◽  
Haiqiang Yang ◽  
Juning Gao ◽  
Yueshan Jiang ◽  
...  
Keyword(s):  
High Temperature ◽  
Carbon Fibers ◽  
Electrochemical Treatment ◽  
Temperature Treatment ◽  
Resistance Test ◽  
High Temperature Treatment ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Before And After ◽  
Spinning Process

Scanning tunneling microscopy (STM) was used to characterize the surface topography of polyacrylonitrile (PAN)-based carbon fibers before and after electrochemical treatment, stretch resistance test, and high-temperature treatment. A new kind of spiral structures was found, which was not only on the surface but also in the inner layer. The spiral structure of the fibers was caused by the spinning process. The fiber structure contained the shape of the precursor. There were some large cracks in the carbon fibers after the stretching resistance test. The large cracks can result in carbon fiber breaking under certain stress conditions. The difference in the structures of the carbon fibers before and after the high-temperature treatment was determined.

scholarly journals Preparation and Characterization of Electrospun PAN/PSA Carbonized Nanofibers: Experiment and Simulation Study

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 821 ◽  
Author(s):  
Shixin Jin ◽  
Jiali Yu ◽  
Yuansheng Zheng ◽  
Wen-Yi Wang ◽  
Binjie Xin ◽  
...  
Keyword(s):  
High Temperature ◽  
Electric Field Distribution ◽  
Fiber Diameter ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
The Finite Element Method ◽  
Before And After ◽  
Nanofiber Membranes ◽  
Scanning Electron

In this study, we simulated the electric field distribution of side-by-side electrospinning by using the finite element method (FEM), and studied the effects of spinneret wall thickness, spinning voltage and receiving distance on the distribution of the electrostatic field. The receiving distance was selected as a variable in the experimental, a series of PAN/PSA composite nanofiber membranes were prepared by using a self-made side by side electrospinning device. The membranes were tested by Fourier-transform infrared (FTIR), thermogravimetric analysis (TG), and scanning electron microscope (SEM). The prepared membranes were also treated by high-temperature treatment, and the change of fiber diameter and conductivity of the membrane before and after high-temperature treatment were studied. It was found that the PAN/PSA carbonized nanofibers could achieve a better performance in heat resistance and conductivity at 200 mm receiving distance.

An experimental study on the fracture behaviors of marble specimens subjected to high temperature treatment

2020 ◽  
Vol 225 ◽  
pp. 106862 ◽  
Author(s):  
Qingzhen Guo ◽  
Haijian Su ◽  
Jiawei Liu ◽  
Qian Yin ◽  
Hongwen Jing ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Temperature ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Fracture Behaviors
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