In this study, graphene oxide (GO), graphene oxide quantum dots (GOQD) and graphene quantum dots (GQD) were synthesized by Hummers, hydrothermal and the calcination in argon methods, respectively. Then the structure of the samples was characterized by X-ray diffraction, Fourier-transform infrared and Raman spectroscopies and their particle size distribution were investigated by dynamic light scattering. Afterward, the electrical and photoelectric properties of the samples were studied by electrical conductivity meter and diffuse reflectance and photoluminescence spectroscopies. Finally, the photoelectrochemical sensors were designed to detect dopamine (DA) based on GO, GOQD and GQD modified glassy carbon electrodes (GCE). The results showed that the sample of GO has graphene plates with widest particle size distribution (about 1.3 to 5.7 µm) and the highest electrical conductivity (287.9 µS/cm). On the other, the sample of GQD has narrowest particle size distribution (about 5.3 to 12.8 nm) and the lowest electrical conductivity (165.1 µS/cm). The samples of GOQD and GQD have light absorption throughout the range of visible wavelength and therefore have photoelectric behavior better than GO. As a result, in DA detection sensors, the photoresponse of the GCEs modified with GOQD and GQD is 4 times higher than that of GO modified GCE. Manuscript profile

The effect of SiC content, additives, and process parameters on densification and microstructural properties of pressureless sintered ZrB2– (1–10 wt %) SiC particulate composites have been studied. The ZrB2–SiC composite powders mixed by Spex mixer with 1-2wt% C (added as graphite powder) and CMC have been cold-compacted and sintered in argon environment in the temperature range of 1800–2100ºC for 2hs. The amount of densification is found to increase with sintering duration and by prior holding at 1200-1650ºC for reduction of oxide impurities (ZrO2, B2O3 and SiO2) on powder particle surfaces via the formation of new phases such as ZrSi2 and ZrC in the system. Presence of SiC with average size smaller than that of ZrB2 appears to aid in densification by enhancing green density, increasing C content by erosion of milling media, and inhibiting matrix grain growth. Both of SiC and C appear to aid in reduction of oxide impurities. The shrinkage of samples was measured, and the microstructure of samples was examined using X-Ray Diffraction and scanning electron microscopy (SEM), equipped with EDS spectroscopy. Room temperature mechanical properties were examined. Sintering temperature has a great effect on relative density, porosity, water absorption, hardness, fracture toughness, oxidation resistance, Strength and microstructure of these composites. The highest relative density, (99.65%), was obtained in ZrB2–10wt. %SiC–2 wt. %C composites sintered at 2000ºC for 2hs. Manuscript profile

In this study, nitrogen and cerium co-doped titanium dioxide nanoparticles were prepared by the sol-gel method and were calcined in air at550 °C for 2 hours. Then, the surface glassy carbon electrode was modified and coated with synthesized nanoparticles. The crystalline structure of the nanoparticles was characterized by X-ray diffraction (XRD). The topography, surface roughness and particle size distribution of the coatings were investigated by atomic force microscopy (AFM). Photoelectric properties such as the changes of the absorption edges and band gap values of the nanoparticles were studied by diffuse reflectance spectra (DRS). The hydrophilic property of the coatings was also measured by a contact angle device. In all of the analyses, the effect of nitrogen doping amount on the characteristics of N, Ce co-doped titania samples was investigated. According to the results, the band gap of the co-doped titania samples relative to that of pure titania has been decreased (from  3.21 eV to  2.78 eV) and their surface hydrophilicity has been improved (from 1.01 (deg.min-1) to 1.60 (deg.min-1)). Among the samples the co-doped titania contains the ratio of Ce/Ti: 1% and N/Ti: 0.25%, has the highest amount of anatase phase ( 93.1%), the lowest agglomeration at the surface, the smallest band gap energy ( 2.78 eV) and the highest photo-induced super-hydrophilicity (hydrophilizing rate: 1.60 (deg.min-1)). Manuscript profile

در این پژوهش، پس از پوشش‌دهی نانوذره‌های مگنتیت با ZnO و TiO2 به روش سل/ژل سعی شد تا تشکیل ساختار و ویژگی مغناطیسی نانوذره‌های هسته/پوسته دو جزیی و سه جزیی با روش پراش پرتو ایکس (XRD)، میکروسکوپ الکترونی عبوری (TEM) و مغناطیس‌سنج ارتعاشی (VSM) بررسی شد. رفتار فتوکاتالیستی در تخریب متیلن به لو در گستره صفر تا 120 دقیقه تحت تابش نور خورشید با طیف‌سنج مرئی/فرابنفش ثبت شد. تغییرات با استفاده از طیف فتولامینسانس (PL) و سطح ویژه به‌دست آمده با دستگاه جذب/واجذب نیتروژن (BET) بررسی شد. نتایج به‌دست آمده نشان داد کهmg/ml 10 نانوذره‌های هسته/پوسته بیش از 90 % از مولکول‌های متیلن به لو را در مدت زمان 120 دقیقه تحت تابش نور خورشید تخریب کرده‌اند. اما افزایش تعداد پوسته‌ها سبب تغییر نوع نیم‌رسانا از نوع مستقیم به غیرمستقیم می‌شود که به دنبال آن فصل مشترک ناهمگن رفتار فتوکاتالیستی را تضعیف می‌کند. Manuscript profile

Manuscript profile

در دو دهه اخیر باتری‌های لیتیم-هوا به علت چگالی انرژی بالا بسیار مورد توجه قرار گرفته‌اند. الکترولیت‌های حالت جامد با هدایت یونی بالا یکی از مهم‌ترین چالش‌ها در ساخت این نوع‌ باتری‌ها به حساب می‌آیند. لیتیم آلومینیوم تیتانیوم فسفات (LATP) نوعی الکترولیت ناسیکونی است که به علت هدایت یونی بالا در باتری‌‌های لیتیم-هوا کاربرد یافته است. هدف از پژوهش حاضر ساخت غشاء هادی یون لیتیم LATP بوده است. به این ترتیب ابتدا پودر LATP به روش شیمیایی سنتز شده و دمای تبلور مناسب با بررسی الگوی پراش نمونه‌ها انتخاب گردید. پس از آن جهت ساخت غشاء نمونه‌ها در دو فشار پرس و دو زمان زینتر متفاوت و در دمای زینتز ℃850 تهیه شدند و اثر این عوامل بر هدایت یونی و دانسیته این نمونه‌ها بررسی گردید. بررسی‌ها نشان دادند که پودر LATP بدون فازهای ناخالصی با روش گفته شده با موفقیت سنتز شد و بهترین کریستالینیتی با آنیل کردن پودر در دمای ℃800 به دست آمد. همچنین بیشترین هدایت یونی به دست آمده مربوط به نمونه پرس شده با فشار Mpa50 و زمان زینتر 3 ساعت و برابر با S.cm-1 10-4×07/1 است. بیشترین دانسیته به دست آمده نیز مربوط به نمونه پرس شده با فشار Mpa50 و زمان زینتر 12 ساعت است. Manuscript profile