Preparation of self-healing hydrogel toward improving electromagnetic interference shielding and energy efficiency

In this study, a self-healing hydrogel was prepared that is transparent to visible (Vis) light while absorbing ultraviolet (UV), infrared (IR), and microwave. The optothermal features of the hydrogel were explored by monitoring temperature using an IR thermometer under an IR source. The hydrogel was synthesized using sodium tetraborate decahydrate (borax) and polyvinyl alcohol (PVA) as raw materials based on a facile thermal route. More significantly, graphene oxide (GO) and graphite-like carbon nitride (g-C3N4) nanostructures as well as carbon microsphere (CMS) were applied as guests to more dissect their influence on the microwave and optical characteristics. The morphology of the fillers was evaluated using field emission scanning electron microscopy (FE-SEM). Fourier transform infrared (FTIR) attested that the chemical functional groups of the hydrogel have been formed and the result of diffuse reflection spectroscopy (DRS) confirmed that the hydrogel absorbs UV while is transparent in Vis light. The achieved result implied that the hydrogel acts as an essential IR absorber due to its functional groups desirable for energy efficiency and harvesting. Interestingly, the achieved results have testified that the self-healing hydrogels had the proper self-healing efficiency and self-healing time. Eventually, microwave absorbing properties and shielding efficiency of the hydrogel, hydrogel/GO, g-C3N4, or CMS were investigated, demonstrating the salient microwave characteristics, originated from the established ionic conductive networks and dipole polarizations. The efficient bandwidth of the hydrogel was as wide as 3.5 GHz with a thickness of 0.65 mm meanwhile its maximum reflection loss was 75.10 dB at 14.50 GHz with 4.55 mm in thickness. Particularly, the hydrogel illustrated total shielding efficiency (SET) > 10 dB from 1.19 to 18 and > 20 dB from 4.37 to 18 GHz with 10.00 mm in thickness. The results open new windows toward improving the shielding and energy efficiency using practical ways.

CARA MUDAH DETEKSI BORAKS MENGGUNAKAN KERTAS SARING UBI JALAR UNGU (KESARING BIJU)

Boraks atau yang lebih dikenal oleh masyarakat dengan nama “bleng” (bahasa jawa) yaitu serbuk kristal lunak yang mengandung boron, berwarna putih atau transparan tidak berbau dan larut dalam air. Boraks dengan dalam nama ilmiahnya dikenal sebagai natrium tetraborate decahydrate. Boraks mempunyai nama lain natrium biborat, natrium piroborat, natrium tetraborat yang seharusnya hanya digunakan dalam industry non pangan. Menurut Kamus Kedokteran Dorland, boraks dikenal sebagai bahanpembasa preparat farmasi. Boraks juga digunakan sebagai bahan bakterisida lemah dan astringen ringan dalam lotion, obat kumur dan pembersih mulut.Boraks juga disebut sebagai sodium pyroborate dan sodium tetraborate.Boraks mempunyai rumus kimia Na2B4O2(H20)10dengan berat molekul 381,43 dan mempunyai kandungan boron sebesar 11,34 %. Boraks bersifat basa lemah dengan pH (9,15 – 9,20). Boraks umumnya larut dalam air, kelarutan boraks berkisar 62,5 g/L pada suhu 25C dan kelarutan boraks dalam air akan meningkat seiring dengan peningkatan suhu air dan boraks tidak larut dalam senyawa alcohol.Adapun peraturan pemerintah yang melarang tentang penggunaan boraks yaitu Peraturan Menteri Kesehatan Republik Indonesia 1168/MENKES/PER/X/1999 yang berisi bahwa boraks termasuk dari salah satu bahan kimia yang penggunaannya dilarang untuk produk makanan karena asam borat dan senyawanya merupakan senyawa kimia yang mempunyai sifat karsinogen. Di dalam oksisitas Boraks dan sejenisnya merupakan pestisida turunan elemen boron. Boron jarang sekali digunakan dalam bentuk tunggal, jenis-jenisnya ditemukan dengan bentuk kombinasi dengan elemen-elemen lain, umumnya dikombinasikan dengan asam borat atau boraks. Tidak seperti beberapa pestisida dengan beberapa komponen sintetik, boraks dan beberapa pestisida secara alami merupakan campuran.Ubi jalar (Ipomoea batatas L.) atau yang biasa dikenal dengan ketela rambat atau “sweet potato” diduga berasal dari benua Amerika. Para ahli Botani dan pertanian memperkirakan daerah asal tanaman ubi jalar adalah daerah Selandia Baru, Polinesia, dan Amerika bagian tengah. Penyebaran ubi jalar pertama kali terjadi ke Spanyol melalui Tahiti, Kepulauan Guam, Fiji, dan Selandia Baru. Orang-orang Spanyol dianggap berjasa menyebarkan ubi jalar ke kawasan Asia, terutama Filipina, Jepang dan Indonesia (Rukmana, 1997). Warna merah dan ungu pada bunga, batang, daun, dan umbi merupakan akibat dari adanya senyawa antosianin. Keberadaan senyawa antosianin pada ubi jalar ungu atau merah dapat berfungsi sebagai komponen pangan sehat dan paling lengkap (Hambali,dkk.2014).

Borax buffer solution for pH measurement: Homogeneity and stability studies and its application in the proficiency testing program

This paper describes the preparation of borax buffer solution and its application as proficiency testing (PT) test samples in a PT scheme. The test samples were made gravimetrically from 0.01 M sodium tetraborate decahydrate and pH of the test samples were measured by using a differential potentiometric cell. Homogeneity and stability of test samples were evaluated in accordance to ISO13528:2015. The results obtained revealed that test samples met the PT requirement criteria in terms of stability and homogeneity. The prepared PT test samples were used in the 2016PT scheme. From the results received from 50 participants, it was found that about 44 % of participants achieved satisfactory results, 38 % achieved unsatisfactory results, while the remaining participants (about 18 %) showed a questionable result.

Development of Cement Solidification Process for Sodium Borate Waste Generated From PWR Plants

A cement solidification process for treating sodium borate waste produced in pressurized water reactor (PWR) plants was studied. To obtain high volume reduction and high mechanical strength of the waste, simulated concentrated borate liquid waste with a sodium / boron (Na/B) mole ratio of 0.27 was dehydrated and powdered by using a wiped film evaporator. To investigate the effect of the Na/B mole ratio on the solidification process, a sodium tetraborate decahydrate reagent with a Na/B mole ratio of 0.5 was also used. Ordinary portland cement (OPC) and some additives were used for the solidificaiton. Solidified cement prepared from powdered waste with a Na/B mole ratio 0.24 and having a high sillica sand content (silica sand/cement>2) showed to improved uniaxial compressive strength.