Tài liệu miễn phí Hoá học
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Chế tạo và xác định đặc tính màng phân hủy sinh học trên cơ sở poly(vinyl alcohol) và chitosan
Bài viết Chế tạo và xác định đặc tính màng phân hủy sinh học trên cơ sở poly(vinyl alcohol) và chitosan trình bày ảnh hưởng hàm lượng chitosan đến độ trương của màng; Ảnh hưởng hàm lượng chitosan đến độ bền kéo đứt của màng.
4/9/2023 11:47:02 AM +00:00
A Raman study of cation-disorder transition temperature of natural \(MgA{l_2}{O_4}\) spinel
In the work A Raman study of cation-disorder transition temperature of natural \(MgA{l_2}{O_4}\) spinel, the author have measured Raman spectra of samples of natural \(MgA{l_2}{O_4}\) spinel before and after annealing at different temperatures and quenching. The appearance of 727 cm 1 mode in the samples annealed at 800oC or higher is believed to be due to the cation-disorder of spinel.
4/9/2023 11:35:17 AM +00:00
Chemical composition of Cinnamomum Cassia oil in Vietnam and its spatial repellent effects against the aedes aegypti
Dengue is a mosquito-borne viral disease that has caused millions of dengue virus infections per year in the world. Mosquito repellent is an effective way to prevent mosquito bites and the spread of mosquito-borne disease. In this study, we extracted essential oil from the bark of Cinnamomum cassia collected in Viet Nam and analyzed its chemical composition.
4/9/2023 10:06:04 AM +00:00
Investigation of thermodynamic equilibria of vitamin C in various solvents via experimental determination and model correlation
Vitamin C plays an essential role in pharmaceutical industry. In general, the solubility of this vitamin in different environments is an important factor for drug development processes. Indeed, solid-liquid equilibrium (SLE) determination of the interested compound in various solvents needs high-precision determination which, however, frequently consumes a lot of time and labor work.
4/9/2023 10:05:34 AM +00:00
Plant flavonoids as potential natural antioxidants in phytocosmetics
Phytocosmetics, the sub-discipline of cosmetology which primarily uses plant and plant extracts in beauty treatments, has been endorsed for thousands of years. After a period of time being pushed aside by an enormous wave of interest in synthetic products, phytocosmetics is slowly but surely returning to its propitious moment.
4/9/2023 10:05:14 AM +00:00
Synthesis and characterization of hybrid nanocomposites of gold nanostars encapsulated on graphene oxide as active sers nanotags
Hybrid nanocomposites of gold nanostars and graphene oxide exhibit intriguing optical and electrical properties derived from the sharp-tip effect of nanostars and the high conductivity of honeycomb structure from C-sp2 hybridization of graphene-based materials.
4/9/2023 10:04:54 AM +00:00
Research for the development of crack in bimetal Al/Cu sheet
In this paper, we only focus on studying the crack development based on force application. In which, this study uses force to make cracks form and develop differently. Specifically, the research focuses on the following contents: surveying the microstructure of the Al/Cu junction, investigating the crack growth.
4/9/2023 10:04:48 AM +00:00
GC-MS analysis the fatty acid components of Tamarindus indica seeds in Vietnam
Tamarindus indica is an edible plant, especially its fruits were wildly used as food or herbs in Vietnam. The seed of Tamarindus indica has been already studied for its phytochemistry and some bioactivities, but there still have limited publications about the fatty acid part of this material.
4/9/2023 10:04:35 AM +00:00
Terminal sliding mode control based on new quasi-sliding mode function for two tanks interacting system
In this paper, a terminal sliding control based on a new quasi-sliding mode function is designed to control a liquid level in two tanks interacting system with external disturbance and uncertainty. This system is always in great demand in the chemical industry, petrochemical refining, water treatment, power generation, construction material production, food processing, automatic liquid dispensing and replenishment devices.
4/9/2023 10:03:58 AM +00:00
Differences between chemical reaction kinetics and adsorption kinetics: Fundamentals and discussion
Adsorption kinetics is an essential part in adsorption studies. The pseudofirst-order (PFO) and pseudo-second-order (PSO) models are frequently used to model the experimental dataset of time-dependent adsorption. The differential equations (based on reaction rate and rate law) of the PFO and PSO models are similar to those of chemical reactions (i.e., first and second order-kinetic reactions).
4/9/2023 10:03:52 AM +00:00
Adhesive strength of hexadecane on different iron compounds: An MD approach
The lubricity of alkane is a research target for numerous tribological applications in either industrial area or fundamental scientific studies. In the current work, a comparative investigation using a classical molecular dynamics (MD) method is carried out to investigate the effect of pure iron and its oxide surfaces on structural properties, adsorption ability of hexadecane (C16H34).
4/9/2023 8:54:56 AM +00:00
Bài giảng Hóa đại cương: Chương 5 - ĐH Nông Lâm TP.HCM
Bài giảng Hóa đại cương - Chương 5: Dung dịch. Chương này gồm có những nội dung chính sau: Một số khái niệm, dung dịch chất điện ly, cân bằng trong dung dịch chất điện ly khó tan. Mời các bạn cùng tham khảo.
4/9/2023 8:11:06 AM +00:00
Bài giảng Hóa đại cương: Chương 4 - ĐH Nông Lâm TP.HCM
Bài giảng Hóa đại cương - Chương 4: Động hóa học. Chương này gồm có những nội dung chính sau: Phương trình động học một số phản ứng đơn giản, các yếu tố ảnh hưởng đến vận tốc phản ứng, cân bằng hóa học, hằng số cân bằng, các yếu tố ảnh hưởng đến cân bằng. Mời các bạn cùng tham khảo.
4/9/2023 8:10:59 AM +00:00
Bài giảng Hóa đại cương: Chương 3 - ĐH Nông Lâm TP.HCM
Bài giảng Hóa đại cương - Chương 3: Nhiệt động hóa học. Chương này gồm có những nội dung chính sau: Các khái niệm cơ bản, nguyên lý 1 của nhiệt động lực học và hiệu ứng nhiệt của quá trình hóa học, nguyên lý thứ 2 của nhiệt động lực học và chiều quá trình hóa học. Mời các bạn cùng tham khảo.
4/9/2023 8:10:53 AM +00:00
Bài giảng Hóa đại cương: Chương 2 - ĐH Nông Lâm TP.HCM
Bài giảng Hóa đại cương - Chương 2: Liên kết hóa học & cấu tạo phân tử. Chương này gồm có những nội dung chính sau: Những khái niệm cơ bản về liên kết hóa học, liên kết cộng hóa trị, liên kết ion, liên kết hyđro, liên kết Van Der Vaal. Mời các bạn cùng tham khảo.
4/9/2023 8:10:41 AM +00:00
Bài giảng Hóa đại cương: Chương 1 - ĐH Nông Lâm TP.HCM
Bài giảng Hóa đại cương - Chương 1: Cấu tạo nguyên tử & bảng phân loại tuần hoàn các nguyên tố hóa học. Chương này gồm có những nội dung chính sau: Sơ lược về các thuyết cấu tạo nguyên tử, thuyết cấu tạo nguyên tử hiện đại theo cơ học lượng tử, bảng hệ thống tuần hoàn các nguyên tố hóa học. Mời các bạn cùng tham khảo.
4/9/2023 8:10:32 AM +00:00
Adsorption behavior of Pb(II) in aqueous solution using coffee husk-based activated carbon modified by nitric acid
In the work Adsorption behavior of Pb(II) in aqueous solution using coffee husk-based activated carbon modified by nitric acid, activated carbon (AC) was prepared from coffee husk and modified by nitric acid for effective lead ions removal from aqueous solution. The as-prepared samples have uniform particles size, developed surface area and contain acidic surface functional groups. Nitric acid modification showed a pronounced effect on improving Pb(II) adsorption capacity. The Freundlich isotherm model and pseudo second-order kinetic model could best describe the adsorption of Pb(II) onto AC-Nitric. Thermodynamics parameters proved the spontaneous, physic and endothermic nature of the adsorption of Pb(II) onto AC-Nitric.
4/9/2023 8:02:56 AM +00:00
Activated Carbon Prepared from Rice Husk: Nitric Acid Modification and BTX Adsorption
The aim of the work Activated Carbon Prepared from Rice Husk: Nitric Acid Modification and BTX Adsorption is to evaluate the elimination of BTX by activated carbons prepared from rice husk. The effects of surface modification on the specific surface area, pore texture and adsorption capacity of the AC samples have been examined.
4/9/2023 8:02:50 AM +00:00
Magnetic Properties and Impedance Spectroscopic Studies of Multiferroic Bi1-xNdxFeO3 Materials
In the paper Magnetic Properties and Impedance Spectroscopic Studies of Multiferroic Bi1-xNdxFeO3 Materials, we report the Nd-doping effect on structural, magnetic, and complex impedance properties of BFO materials. With the presence of Nd, the crystal structure of BFO was changed. Weak ferromagnetism was observed with an enhancement of spontaneous magnetization due to the collapse of the spin cycloid structure.
4/9/2023 8:02:19 AM +00:00
Magnetic chitosan nanoparticles for removal of Cr(VI) from aqueous solution
In the paper Magnetic chitosan nanoparticles for removal of Cr(VI) from aqueous solution, magnetic chitosan nanoparticles were prepared, characterized and applied for the removal of Cr(VI) in the water solution. Afterwards, thermodynamic and kinetic aspects of the adsorption process were considered. The improved magnetic and high adsorption uptake properties are two main features of the synthesized nanoparticles that can be advantageously used in water treatment.
4/9/2023 8:02:12 AM +00:00
A study on carbon nanotube titanium dioxide hybrids: experiment and calculation
The study A study on carbon nanotube titanium dioxide hybrids: experiment and calculation report synthesis of TiO2/CNTs composite by simple grinding method and study improving their photocatalytic activity under visible light. The photocatalytic activities of samples were assessed by photodegradation of methylene blue (MB). We have investigated the geometry and electronic structure of small TiO2 clusters adsorbed on singlewall carbon nanotubes (SWCNTs) support using first-principles density functional calculations. We discuss the interfacial electronic structures and electron transfer of CNT interfaced with TiO2 clusters.
4/9/2023 8:02:05 AM +00:00
The photoluminescence enhancement of Mn2+ ions and the crystal field in ZnS:Mn nanoparticles covered by polyvinyl alcohol
The paper The photoluminescence enhancement of Mn2+ ions and the crystal field in ZnS:Mn nanoparticles covered by polyvinyl alcohol report the synthesis of ZnS:Mn/PVA nanoparticles by second method, in which PVA solution is mixed from the beginning with the initial solutions used to synthesize ZnS:Mn nanoparticles. The microstructures, morphology of ZnS:Mn/PVA nanoparticles, the PL enhancement of Mn2? ions by different PVA mass, the absorption and radiation transitions in the ZnS:Mn crystals and the crystal field strength Dq are investigated and explained.
4/9/2023 8:01:58 AM +00:00
Fabrication of Mn-Bi Nanoparticles by High Energy Ball Milling
The MnBi low temperature phase with high value and positive temperature coefficient of its coercivity has a potential for production of both the nanocomposite and hybrid permanent magnets. The report Fabrication of Mn-Bi Nanoparticles by High Energy Ball Milling present our results of investigation of fabrication of Mn55Bi45 nanoparticles by using high energy ball milling method.
4/9/2023 8:01:25 AM +00:00
Effects of Mn, Cu doping concentration to the properties of magnetic nanoparticles and arsenic adsorption capacity in wastewater
In this paper Effects of Mn, Cu doping concentration to the properties of magnetic nanoparticles and arsenic adsorption capacity in wastewater present the studying results of the synthesize process, the magnetic properties, microstructure, surface properties of Mn, Cu doped Fe3O4 nanomaterials and the influence of Mn, Cu concentrations on the arsenic adsorption process in water at different pH.
4/9/2023 8:01:19 AM +00:00
Kinetics of the Hydrogenation of a Mixture of Nitrobenzene and Azoxybenzene on Skeletal Nickel in an Aqueous Solution of Propan-2-ol
The aim of the work Kinetics of the Hydrogenation of a Mixture of Nitrobenzene and Azoxybenzene on Skeletal Nickel in an Aqueous Solution of Propan-2-ol was to reveal the sequence of the reduction of nitrobenzene (NB) and azoxybenzene (AB) on skeletal nickel for their combined presence in aqueous solutions of propan-2-ol of different compositions.
4/9/2023 8:01:03 AM +00:00
Planar Geometry of 4-Substituted-2,2'-bipyridines Synthesized by Sonogashira and Suzuki Cross-Coupling Reactions
In the paper Planar Geometry of 4-Substituted-2,2'-bipyridines Synthesized by Sonogashira and Suzuki Cross-Coupling Reactions, we report the synthesis, geometry and molecular arrangement in the crystals of two compounds, namely 4-(ferrocenylethynyl)-2,2'-bipyridine (I) and 4-ferrocenyl-2,2'-bipyridine (II) which were synthesized by the palladium catalyzed Sonogashira [5, 6] and Suzuki-Miyaura [7, 8] cross-coupling reactions.
4/9/2023 8:00:50 AM +00:00
Theoretical Study on \(R{u^{2 + }}, C{u^ + }, and F{e^{2 + }}\) Complexes Toward the Application in Dye Sensitized Solar Cell
This paper reports the application of the \(R{u^{2 + }}, C{u^ + }, and F{e^{2 + }}\) complexes in form of RuL2(SCN)2, CuL2(SCN)2 for dye-sensitized solar cell (DSSC) development. The calculation results, given by quantum chemistry, demonstrated that the complex containing copper is more suitable than the one containing iron. The modification of Cu(I) complex by using various numbers of ligands enhanced photon absorption capacity as well as the absorption range.
4/9/2023 8:00:38 AM +00:00
Theoretical Study on the Adsorption of Carbon Dioxide on Individual and Alkali-Metal Doped MOF-5s1
Density functional theory (DFT) calculations were performed to investigate the adsorption of carbon dioxide (CO2) on metal-organic framework (MOF-5) and alkali-metal (Li, K, Na) doped MOF-5s. The adsorption energy calculation showed that metal atom adsorption is exothermic in MOF-5 system. Moreover, alkali-metal doping can significantly improve the adsorption ability of carbon dioxide on MOF-5. The best influence is observed for Li-doping.
4/9/2023 8:00:22 AM +00:00
Theoretical study of carbon dioxide activation by metals (Co, Cu, Ni) supported on activated carbon
The activation of carbon dioxide (CO2) by catalytic systems comprising a transition metal (Co, Cu,Ni) on an activated carbon (AC) support was investigated using a combination of different theoretical calculation methods: Monte Carlo simulation, DFT and DFT-D, molecular dynamics (MD), and a climbing image nudged elastic band (CI-NEB) method. The results obtained indicate that CO2 is easily adsorbed by AC or MAC (M: Cu, Co, Ni).
4/9/2023 8:00:15 AM +00:00
New provincial records of skinks (Squamata: Scincidae) from northwestern Vietnam
In this paper New provincial records of skinks (Squamata: Scincidae) from northwestern Vietnam, we report six new records of skinks from northwestern Vietnam: Eutropis macularius, Scincella devorator, S. monticola, S. ochracea, Sphenomorphus cryptotis and S. indicus. Our new findings increase the species number of skinks (Scincidae) to nine in Dien Bien Province and to 14 in Son La Province. We also provide additional natural history data of aforementioned species.
4/9/2023 7:59:07 AM +00:00