scholarly journals Структурный переход и температурные зависимости коэффициентов теплового расширения NaNO-=SUB=-3-=/SUB=-, внедренного в нанопористое стекло

2022 ◽  
Vol 64 (3) ◽  
pp. 365
Author(s):  
А.А. Набережнов ◽  
О.А. Алексеева ◽  
А.В. Кудрявцева ◽  
Д.Ю. Чернышов ◽  
Т.Ю. Вергентьев ◽  
...  
Keyword(s):  
Critical Exponent ◽  
Sodium Nitrate ◽  
Coefficient Of Thermal Expansion ◽  
Bulk Material ◽  
Average Pore ◽  
Linear Coefficient ◽  
Temperature Range ◽  
Orientational Transition ◽  
Significant Difference ◽  
Average Size

The temperature evolution of the crystal structure of a nanocomposite material obtained by introducing sodium nitrate NaNO3 from a melt under pressure into a nanoporous alkali borosilicate glass with an average pore diameter of 7 nm has been studied by the method of diffraction of synchrotron radiation in a wide temperature range upon heating. Analysis of the experimental diffraction patterns revealed a significant decrease in the temperature of the structural (orientational) transition by more than 50 K (up to 496 K) compared to bulk sodium nitrate. From the temperature dependence of the intensity of the superstructure peak (113), the dependence of the critical exponent β (T) for this transition was obtained and a significant difference from the critical exponent for a bulk material was found in the temperature range from 455 K to the transition temperature. Analysis of the broadening of Bragg reflections made it possible to estimate the average size (~ 40 nm) of sodium nitrate nanoparticles into the pores. An increase in the linear coefficient of thermal expansion in the [001] direction was found in NaNO3 nanoparticles in comparison with bulk material at temperatures above 450 K.

scholarly journals Тепловое расширение кристаллов Pb-=SUB=-1-x-=/SUB=-Cd-=SUB=-x-=/SUB=-Te

2021 ◽  
Vol 55 (12) ◽  
pp. 1216
Author(s):  
М.К. Шаров
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Solid Solutions ◽  
Coefficient Of Thermal Expansion ◽  
Cadmium Content ◽  
Lattice Period ◽  
Linear Coefficient ◽  
X Ray ◽  
Temperature Range

The values of the lattice period and the linear coefficient of thermal expansion (alfa) of Pb1-xCdxTe solid solutions are determined depending on the cadmium content and temperature using high-temperature X-ray diffractometry. Аn increase in the concentration of cadmium in Pb1-xCdxTe in the range x = 0.02–0.08 leads to a significant increase in the linear coefficient of thermal expansion. A change in temperature range T = 293–673 K leads to decrease in the linear coefficient of thermal expansion. Besides, an increase in temperature does not affect the value alfa of the undoped PbTe in the indicated temperature range.

Properties of AlN-Based Magnesium-Matrix Composites Produced by Pressureless Infiltration

2006 ◽  
Vol 509 ◽  
pp. 105-110 ◽  
Author(s):  
C.A. León ◽  
Y. Arroyo ◽  
E. Bedolla ◽  
E.A. Aguilar ◽  
Robin A.L. Drew
Keyword(s):  
Tensile Strength ◽  
Coefficient Of Thermal Expansion ◽  
General Rule ◽  
Infiltration Rate ◽  
Test Method ◽  
Pressureless Infiltration ◽  
Metal Composite ◽  
Linear Coefficient ◽  
Temperature Range ◽  
Shear Punch Test

A novel ceramic-metal composite with continuous interconnected ceramic and metal phases has been fabricated from sintered porous particulate AlN preforms infiltrated with magnesium. The 48 vol. % AlN composites are fabricated by pressureless infiltration in argon in the temperature range of 870 °C to 960 °C. An increase in the infiltration rate is observed as the temperature increases. Results on the mechanical characterization of the composites indicate an elastic modulus of 90 to 110 GPa and hardness of 70 to 80 HRB. The tensile strength calculated by the shear punch test method ranges from 260 to 390 MPa. As a general rule, it is observed that the lower the infiltration temperature, the higher the tensile strength. The linear coefficient of thermal expansion of the infiltrated composites in the temperature range of 215 to 315 °C is 7.65 x 10-6 °C-1. This value is lower than those found for similar Al/AlN composites reported in the literature.

INVESTIGATION OF BIAXIAL ELASTIC MODULUS AND CTE OF BaTiO3 FILMS

2009 ◽  
Vol 23 (24) ◽  
pp. 4933-4941
Author(s):  
GUI-FANG HUANG ◽  
WEI-QING HUANG ◽  
LING-LING WANG ◽  
ZHONG XIE ◽  
BING-SUO ZOU ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Thermal Cycle ◽  
Laser Scanning ◽  
Stress Measurement ◽  
Coefficient Of Thermal Expansion ◽  
Bulk Material ◽  
Good Reliability ◽  
Scanning Method ◽  
As Stress

To develop high-quality film device with good reliability, it is often essential to be able to evaluate the parameters such as stress, the biaxial elastic modulus, and coefficient of thermal expansion (CTE) of film. Based on the stress measurement in situ during the thermal cycle by laser scanning method, two techniques were used to measure the biaxial elastic modulus and CTE of BaTiO 3 films deposited on substrate. The value of the biaxial elastic modulus and CTE for BaTiO 3 films determined from two methods is close, in which the biaxial elastic modulus of BaTiO 3 films is higher than that of corresponding bulk while the CTE of BaTiO 3 films is a little smaller than that of bulk material.

Comparison of High Temperature Mechanical Behaviour and Microstructure of the New Gamma–TiAl8Ta with Gamma-TiAl8Nb Alloy

2010 ◽  
Vol 72 ◽  
pp. 40-45
Author(s):  
Giuliano Angella ◽  
Valentino Lupinc ◽  
Maurizio Maldini ◽  
Giovanni Onofrio
Keyword(s):  
High Temperature ◽  
Mechanical Behaviour ◽  
Low Cycle Fatigue ◽  
Fatigue Properties ◽  
Stress Intensity Factor Range ◽  
Fatigue Crack Propagation Rate ◽  
Difference Threshold ◽  
Temperature Range ◽  
R Ratio ◽  
Significant Difference

The high temperature creep and fatigue properties of two  -TiAl base intermetallic alloys, for gas turbine components, have been investigated within the Integrated European project IMPRESS. The alloys contain 8% at. of Ta or Nb, respectively. The microstructure of both alloys was cross convoluted lamellar rather than the well known conventional lamellar, typical of the usual -TiAl. The microstructure of the Ta containing alloy was homogeneous in all the analyzed batches whilst that of the Nb alloy appeared significantly spread out from specimen to specimen. The creep properties of the alloys were investigated in the temperature range 700-850°C with applied stresses in order to have times to rupture up to about 3,000 h. The creep behaviour presented no steady state regimes, but only minima of the creep rates between significant decelerating and accelerating regimes. The minimum creep rates of the Ta alloy resulted to be significantly slower than the Niobium alloy at the same creep conditions. In low cycle fatigue at 650 and 700°C the Ta  -TiAl showed longer lives than the Nb alloy, whilst the fatigue crack propagation rate in the same temperature range did not show any significant difference. Threshold values of stress intensity factor range were accurately measured at different R ratio. The microstructures of the two alloys were analysed by scanning microscopy in order to rationalise the different mechanical behaviour.

scholarly journals Fracture of Be and Its Alloys - Webb Space Telescope Revisited

2021 ◽  
Author(s):  
Muhammad Musaddique Ali Rafique
Keyword(s):  
Near Infrared ◽  
Joint Venture ◽  
Coefficient Of Thermal Expansion ◽  
Infrared Range ◽  
Linear Coefficient ◽  
Space Telescope ◽  
Hexagonal Close Packed ◽  
James Webb Space Telescope ◽  
Layer Deposition ◽  
Slip Planes

NASA/ESA/CSA joint venture James Webb Space Telescope is about to be launched. It is hypothesized to operate in near-infrared range. It is also hypothesized to unveil early star formation, galaxies, and universe due to its orbit, point in orbit and orbital motion. It has been under manufacturing for over 20 years at a staggering cost of 10 billion US dollars (most expensive scientific experiment in history). Beryllium (Be) is chosen to be element for construction of its main mirrors due to its high stiffness, low density, low linear coefficient of thermal expansion (α) in cryogenics and high thermal conductivity. It is followed by gold (Au) layer deposition on its (Be) surface to enhance its sensitivity towards infrared radiation as later is hypothesized to bear superior properties. However, serious mistakes have been made in selecting this material for this application. Owing to its crystal structure (hexagonal close packed (hcp)), slip planes (basal, prismatic and pyramidal) and mechanisms of their activation, Be necessitates easy fracture at cryogenic temperature. It has anisotropic properties and prone to transverse fracture under tensile loading. Furthermore, its ductile to brittle transition temperature is very low making it entirely unsuitable for such an application. It is one of most expensive metals on planet. This study constitutes revisiting these fundamental properties and mechanisms which were entirely ignored during materials selection thus rendering whole project useless.

scholarly journals Clinico-radiological profile of abdominal tuberculosis in HIV/AIDS patients-a study from rural central India

2017 ◽  
Vol 5 (5) ◽  
pp. 1980 ◽  
Author(s):  
Nisar A. Wafai ◽  
Sudhir K. Yadav ◽  
Prem S. Singh ◽  
Manoj Kumar ◽  
Prafulla K. Singh ◽  
...  
Keyword(s):  
Imaging Modality ◽  
Central India ◽  
Abdominal Tuberculosis ◽  
Cd4 Count ◽  
Common Finding ◽  
Non Invasive ◽  
Significant Difference ◽  
Average Size ◽  
Loss Of Appetite ◽  
Hiv Aids

Background: One of the major challenge of present era is dual epidemic of HIV/AIDS and tuberculosis. With immunosuppression, risk of opportunistic diseases increases in these patients and tuberculosis is most common opportunistic infection. The prevalence of abdominal tuberculosis seems to be rising, particularly due to increasing prevalence of HIV infection. The diagnosis of abdominal tuberculosis can often be difficult and it remains underdiagnosed, in view of its nonspecific manifestations. The investigations involved in its diagnosis are expensive and time consuming, however, ultrasonography (USG) is an affordable, non-invasive and widely available modality which can be of help in the diagnosis of abdominal tuberculosis. Therefore, this study was undertaken to evaluate clinical and USG finding among Abdominal Tuberculosis patients with HIV/AIDS.Methods: After informed consent, patients underwent thorough history taking and clinical examination followed by high quality USG abdomen and other biochemical and haematological tests including CD4 count. Follow up USG abdomen was done at time of completion of course of ATT and data was analysed.Results: 45 were found to have abdominal tuberculosis. Of these patients, 31(68.9%) were male and 14 (31.1%) were female. Mean age of HIV-abdominal TB was 34.27±9.66 years. most common symptoms were weight loss 41(91.1%), loss of appetite 38(84.4%), fever       32(71.1%), generalized weakness 30(66.7%) and abdominal pain 27(60.0%). On USG abdomen, intraabdominal lymphadenopathy was most common finding found in 44(97.8%). Average size of enlarged lymph node was 3.1+-1.0 cm. Mesenteric lymphnodes were enlarge in 40(88.89%), paraaortic 8(17.78%), retroperitoneal 4(8.89%) while peripancreatic and porta hepatic in 3(6.67%). splenomegaly was noted in 14(31.1%) cases. Hepatomegaly was found in 6 cases, who all were male. Ascites was evident in 5(11.1%) patients. Extensive involvement, defined as involvement of two or more intraabdominal sites, was found 24(53.3%) cases. There was no statistically significant difference found among these USG findings and CD4 count.Conclusions: The findings of lymphadenopathy (size>15mm) and hypoechoic/necrotic echotexture, hepatosplenomegaly with hypoechoic lesions in ultrasonography are suggestive of abdominal tuberculosis in HIV infected patients with unexplained nonspecific symptoms and low CD4 count.  However, above findings are not standardized and inability to confirm the diagnosis of tuberculosis by direct microscopy and culture is the limitation of this study. Ultrasonography is an affordable, widely available, non-invasive imaging modality which may be optimally utilized for the diagnosis of abdominal tuberculosis in HIV infected patients, especially in the rural setup where microbiological and other sophisticated radiological investigations have limited availability.

scholarly journals Detailed Thermal Characterization of Acrylonitrile Butadiene Styrene and Polylactic Acid Based Carbon Composites Used in Additive Manufacturing

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2960
Author(s):  
Zoltan Ujfalusi ◽  
Attila Pentek ◽  
Roland Told ◽  
Adam Schiffer ◽  
Miklos Nyitrai ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
3D Printing ◽  
Thermal Hysteresis ◽  
Acrylonitrile Butadiene Styrene ◽  
Thermal Characterization ◽  
Carbon Composites ◽  
Biomedical Sensors ◽  
Temperature Range ◽  
Ohmic Resistance ◽  
Significant Difference

Currently, 3D printing is an affordable technology for industry, healthcare, and individuals. Understanding the mechanical properties and thermoplastic behaviour of the composites is critical for the users. Our results give guidance for certain target groups including professionals in the field of additive manufacturing for biomedical components with in-depth characterisation of the examined commercially available ABS and PLA carbon-based composites. The study aimed to characterize these materials in terms of thermal behaviour and structure. The result of the heating-cooling loops is the thermal hysteresis effect of Ohmic resistance with its accommodation property in the temperature range of 20–84 °C for ESD-ABS and 20–72 °C for ESD-PLA. DSC-TGA measurements showed that the carbon content of the examined ESD samples is ~10–20% (m/m) and there is no significant difference in the thermodynamic behaviour of the basic ABS/PLA samples and their ESD compounds within the temperature range typically used for 3D printing. The results support the detailed design process of 3D-printed electrical components and prove that ABS and PLA carbon composites are suitable for prototyping and the production of biomedical sensors.

Effects of Modification and Heat Treatment on Microstructure and Mechanical Property of Two-Step Foamed ZL111 Alloy Foam

2018 ◽  
Vol 933 ◽  
pp. 68-77
Author(s):  
Yu Yuan Jiang ◽  
Xiao Xu Luo ◽  
Qing Chen ◽  
Ming Wei Zhao ◽  
Jian Sheng Lu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Mechanical Property ◽  
Eutectic Silicon ◽  
Absorption Capacity ◽  
Compressive Property ◽  
Average Pore ◽  
T6 Heat Treatment ◽  
Sr Modification ◽  
Average Size ◽  
Microstructure And Mechanical Property

ZL111 alloy foams with a porosity of 80% and an average pore diameter of 3.5 mm were fabricated using a two-step foaming process, and the effects of modification and heat treatment on their microstructure and mechanical property were studied. The results indicates that by Y&Sr modification, most of the eutectic silicon in the ZL111 alloy foam is transformed from plate-like into dot-like forms, and the average size of evenly distributed α-Al grain is reduced from 80~100μm to 30~40μm, which is more efficient than separate Y or Sr modifications. By combining Y and Sr modification and T6 heat treatment, the α-Al grain size of ZL111 alloy foam maintains its previous modified effect, eutectic silicon remains spherical and well-distributed, and CuAl2and Al9FeMg3Si5are dispersed homogeneously at the α-Al grain boundary. The Y&Sr modification and T6 heat treatment also significantly improved the compressive property of ZL111 alloy foam, when we compared them with the untreated ZL111 alloy foam. The compressive strength rises from 13.3 MPa to 22.6 MPa, the densification strain improves from 59.3% to 76.9%, and the energy absorption capacity increases from 4.87 MJ/m3to 13.77 MJ/m3.

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