Papers by Keyword: Chemistry

Abstract: This study was conducted to determine the responses of chemistry teachers in providing chemistry experiments and managing chemistry laboratories. A purposive survey method was used in this study by giving online questionnaires through google forms. A total of 30 chemistry teachers from Jakarta area had participated in this survey and 5 of them were selected to be interviewed. The research found challenges that chemistry teachers have tried to utilize various references technology platforms in conducting learning since pandemic Covid-19 affected although the majority of them have never participated in training, the assistance from laboratory technician in managing school laboratory is still low, laboratory facilities in some schools are still not adequate, time allocation is often limited to carry out chemistry experiments in the laboratory. These challenges focus on the problem of human resources, laboratory facilities, and the content of chemistry experiments that related to time allocation. Therefore, this is the right opportunity to think about the development and implementation of chemistry laboratory information system in high schools now and in the future.

Abstract: Manganese oxide and metallic manganese have made a long and varied contribution to the production of iron and steel through the centuries, long before Sir Robert Hadfield’s alloy manganese steel first produced in 1882. Although quite well known empirically, this contribution has sometimes been misunderstood or misrepresented.The success of some of the early so-called ‘natural steels’ was the presence of manganese oxides in the iron ores used.Manganese oxide was already used as a flux from the early days of the production of crucible steel in Asia and it now appears that it was used as a flux from the inception of the otherwise very different later European crucible steel technologies. After the introduction of crucible steel making in Britain in the 18^th century, foreign competitors believed that the reason for the success of the processes used at Sheffield was a secret flux and studies on recently discovered 18^th century crucibles in Sheffield have shown that process was indeed fluxed with manganese oxide.The function of manganese in the later European crucible steel industry has been rather overshadowed and confused historically by the very different ‘Carburet of manganese’, a strange concoction, patented by Josiah Heath in 1839 added to iron or steel to purify the metal. At the time the chemistry of the process was misunderstood and many acrimonious and inaccurate claims were made, crucially confusing the very different functions of manganese oxide and manganese metal, overshadowing the part already played by manganese oxide for almost a century previously..Finally manganese and its salts played a crucial role in the Bessemer process of steel making.

Abstract: Understanding the chemistry in CVD of SiC is important to be able to control, improve and scale up the process to become industrially competitive. A thorough understanding have so far been difficult to achieve due to the complex nature of the process. Through modeling tools, and a systematic approach when constructing the chemical models, new insights to the SiC CVD chemistry can be obtained. Using a general model that is independent on the choice of precursors and reactor configuration, and by coupling modeling results to experimental findings, we here show that SiCl₂ and SiH₂ previously suggested as the main silicon bearing growth species in the chlorinated and standard chemistries, respectively, does not contribute significantly to the SiC growth, and that the main active species are C₂H₂, CH₃, Si, and SiCl.

Abstract: This paper introduces the characteristics and application of polybutylene terephthalate, and then focus on the researches to remove its disadvantages. On this basis, we discuss the influence of different modification methods on the properties of polybutylene terephthalate, and the prospect of the modification has been described as well.

Abstract: General aspects of different gamma ray Compton scattering techniques are introduced. Comparison between the performances of different Compton spectrometers in terms of the parameters: resolution, statistical accuracy, and signal-to-noise ratio are presented. In addition to that, the most relevant parameters for further improvement in the quality of Compton profile measurements are suggested.

Abstract: Compton profile measurement of iron polycrystalline sample has been performed with 662 keV γ-radiation from a caesium-137 source. The spectrometer calibration and data corrections for the high energy experiment are discussed. The data are compared with the augmented-plane-wave (APW) and linear combination of atomic orbitals (LCAO) band theoretical Compton profiles of iron. Both theoretical predictions show the band theories overestimate the momentum density at low momenta and underestimate it at intermediate momenta.

Abstract: AIM: To study the chemical constituents of Euphorbia helioscopia. METHODS: Compounds 1-10 were isolated and purified by silica gel, Sephadex LH-20 and Rp-18 chromatogarphy. Their structures were elucidated mainly by spectroscopic methods. RESULTS: Ten known compounds, helioscopinolide A(1), helioscopinolide B(2), scopoletin(3), scoparone(4), isoscopoletin(5), licochalone A(6), quercelin(7), 7, 4’-dihydroxy-5-methoxy flacanone(8), 2’, 4’-dihydroxy-6’-methoxydihydrochalcone(9) and pinocembrin(10), were isolated and structurally elucidated. CONCLUSION: Compound 3-5 and 8-10 were isolated from this plant for the first time. 2D NMR spectrum data of 2 were also reported in this paper.

Abstract: In order to make students master the basic knowledge of chemistry and skills and learn from the chemical perspective to observe things, thinking, and arouse their interest and desire for learning chemistry, the paper discussed several effective ways of creating studying situation according to the author's years of teaching practice. The ways include stimulating students' interest in study with interest into landscape, enlightening and animating students thinking by the question into view, cultivating students' scientific literacy with exploration into the scene, entering into the searching by the objection into scene, creating the imaginary space with associating into the scene, linking theory with practice by practice into the scene, and improving the learning efficiency by using emotion into the scene.