In recent years, the use of nanotechnology (nanoparticles, nanomaterials and nanoadditives) has attracted the attention of scholars, engineers and scientists across scientific fields such as chemistry , medicine, materials, agriculture, electricity, etc. The use of nanotechnology has also become widespread in refractory products (mainly used by various industries such as steel, casting, cement, glass, etc.). Therefore, many researchers have evaluated the effect of using different types and contents of nanomaterials (oxides and non-oxides) on the properties of formed (bricks) and unformed (monolithic) refractory products and have obtained very interesting results. One of the most consumable refractory products in various industries are monolithic refractories, which are widely used due to their great advantages over other refractory products (bricks). Therefore, recent advances in monolithic refractories made by nanotechnology are presented in this article. This article can be regarded as a comprehensive reference and guide for researchers, students and craftsmen for easy access to experimental research results on the impact of nanotechnology on monolithic refractories. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Nanotechnology (Introduction) The phrase nanotechnology which originates from two words is composed of the Greek numeric prefix nano which refers to a billionth and the word technological [1- 3].Accordingly, nanotechnology or nanoscale technology is commonly considered to be less than 100 nm in size (one nanometer is 10-9 m) [1-2]. According to ASTM C 71, refractories are "nonmetallic materials having those physical and chemical properties which make them applicable for structures or as system components exposed to environments above 1000°F (538°C) [11, 16]. Furthermore, some references mention that refractories are non-metallic inorganic materials that can withstand high temperatures without changing their chemical or physical properties. while remaining in contact with molten waste, metals and gases [11-13, 16-20]. depending on the operational situation, they should have high resistance to thermal shock, be chemically inert and have defined ranges of thermal conductivity and coefficient of thermal expansion[ 11-21, 22]. It is clear that refractories have an important role in the glass, metallurgical and ceramic industries, where they are generated in a variety of shapes to line the interiors of furnaces or other devices for processing materials at high temperatures [23-25] . Some of the inventions and technological and scientific advances would not have been possible without refractory materials. Producing 1 kg of any metal without using refractory material is almost completely impractical [26-29]. The history of using refractory materials dates back to when humanity began to develop the metallurgical process. The first raw material of the refractor was clay. Until the 19th century, refractory products were made from natural minerals, such as magnesite, dolomite and clay. It was in the late 18th and early 19th centuries that the foundations of modern metal beneficiation were laid, the development of Portland cement and modern glass processes began to place higher demands on the refractory industry [30 -33]. The main materials used in the production of refractories are based on Fig.1 [34-36]. In recent years, with the changing trends in steel production, high-performance shaped refractories are increasingly in demand. The longer duration of the campaign and the mutability of new steel production operations are determinedby the accessibility and performance of such shaped refractories with superior high temperature mechanical strength, erosion and corrosion resistance. The selection of refractories to be used is often based on the prevailing conditions in the application area [36-40]. Generally, refractories are divided based on chemical composition, production method and physical form or based on their applications (Fig.2) [11-20, 40 -55]. Based on chemical composition: Acid refractories: these types of refractories are used in regions where the waste and atmosphere are acidic. They have high resistance to acids but are corroded by alkalis. The main raw materials belong to the RO2 category, such as SiO2, ZrO2 etc. Neutral Refractories: These categories of refractories are used in areas where the atmosphere and waste are chemically resistant to both acids and bases. The main raw materials concern, but are not limited to, the R2O3 category. General examples of these materials are Al2O3, Cr2O3, and carbon(C).Basic Refractories: These categories of refractories are used in areas where the atmosphere and waste are basic; these categories have high resistance to alkaline but acid-corroded materials. The main raw materials related to the RO category of which MgO is a very general example. Furthermore, (Mg.Ca(CO3)2 and (MgO-Cr2O3) fall into these categories According to production method: Dry press. Cast casting. Hand-shaped. Formed (plain, fired or chemically bonded). Unformed ( monolithic - plastic, tamping mass and gun, castable).According to physical form:Format: These types have certain shapes and sizes. These types are divided into standard shapes and special shapes. The first type has dimensions confirmed by most refractory manufacturers and is generally suitable for ovens or ovens of the same type. The second type is made specifically for ovens or special ovens: these categories do not have a clear format and are only given the shape on request. Unformed are known as monolithic refractories. Common examples of castables are plastic masses, firing masses, ramming masses, mortars, etc. The phrase monolithic refractory is the name usually given to all unformed refractories. products, the word “monolithic” extracted from the word monolith meaning 'large stone'[56-58]. Monolithic refractories are specific batches or blends of dry granular or cohesive plastic materials used to form nearly seamless linings. Monolithic refractories are unshaped products that are installed as a kind of slurry that eventually hardens to create a solid shape. Most monolithic formulations consist of three constituents such as: large refractory particulates (an aggregate), fine fillers (which fill the voids between the particles), and a binding phase (which gels the particulates together in the green state) Fig 3 [59-65]. Monolithic refractories display a wide range of mineral compositions and vary greatly in their physical and chemical properties. Some of them have a low melting point (low refractoriness), while others approach the compositions of high purity bricks in their ability to tolerate harsh environments. Monolithic refractories are replacing conventional fired refractories at a much faster rate in many applications, including industrial furnaces [53-55, 66-68]. These refractories are used with advantage over brick construction in several types of furnaces. Their use improved the speed of installation. The use of monolithic refractory materials often eliminates difficult brick laying tasks, which can be accompanied by looseness in construction.Furnace protection is very important because substantial repairs can be made with minimal loss of time [69-74]. Sometimes, monolithic refractory linings of the same composition as the firebrick provide better insulation, less diffusion, and greater chipping resistance to the effects of repetitive thermal shock. Other important advantages of monolithic refractory linings are the following [75-80]: ü Removal of joints that represent an intrinsic weakness. ü Easier and faster application. ü Better properties than pressed bricks (sintered or tempered). ü Easier transport and handling. ü Better volume stability. üPossibility of installation in hot standby state. ü Greater mechanical resistance to vibrations and impacts. ü Confirmation of withdrawal and expansion of the application. Different methods are used in the placement of monolithic refractories such as casting, spraying, gun, sand slinging, etc. Monolithic heat-set refractories have very low cold strength values ​​and rely on relatively high temperatures to progress a ceramic bond [81-83]. Since the kiln wall has the usual temperature drop across its thickness, the temperature in the coldest part is generally not sufficient to progress the ceramic bond. However, with the use of a suitable insulating material as a support, the temperature of the coating can be high enough to progress a ceramic bond throughout its thickness. For installation and curing, monolithic refractories require a carefully controlled drying program. This resulted in the filler, binder and aggregate catching fire generating a high strength material [84-86]. Usually monolithic refractories are divided according to Fig.4 [56-60, 65-88] Materials with hydraulic setting in nature are called Castable. These refractories contain a cementitious binder (commonly aluminized cement), which creates hydraulic setting properties when mixed with water. Due to the heating temperature, the material and binder transform or volatilize making it easier to generate a ceramic bond. The most common binder used in castables is high alumina cement. Other binders consist of hydratable alumina and colloidal silica. These materials are installed by pouring and are also known as refractory concretes. Insulating castables are specialized monolithic refractories that are used on the cold surfaces of applications. These monolithic castables are composed of lightweight aggregate aggregates such as vermiculite, bubbled alumina, perlite and expanded clay. The main function of castables is to create thermal insulation. Furthermore, they generally have low density and low thermal conductivity. Castables are classified according to the following [48-58]: ü Conventional castable. ü Castable with low cement content (LCC). ü Castable with very low cement content (ULCC). ü Absence of castable cement (NCC). ü Lightweight castables. ü Self-flow castable (SFC). ü Insulating castable.Plastic refractories are used to form monolithic refractory linings in different types of furnaces. These refractories are suitable for making quick and economical emergency repairs and can be easily rammed into any shape or contour. Plastic refractories consist of refractory aggregates and adhesive clays prepared under rigid plastic conditions with the proper consistency for use without further preparation. During use, the blocks are broken into pieces and are tamped or cast into place with a pneumatic rammer. These refractories can also be cast inwork with a mallet. These refractories are suitable for many important applications due to the high melting point (high refractoriness), the range of compositions and the ease with which the plastic refractories are snapped into place. Additionally, they are often highly resistant to chipping. Plastic refractories can be made from all types of graphite clay, fireclay, high alumina, high alumina graphite and chromium suitable for many different operational situations. Specific shot types are also accessible. These are in granulated form and are produced in the right consistency, ready to use. Some examples of plastic refractory materials are [65-69, 76-80]: ü Super heat-setting refractory plastic, ü Super heat-setting plastic with graphite, ü Plastics in the 50% alumina class, ü 60% alumina class plastic heat-setting, ü Air-fixed high-alumina plastics with alumina class 80%, ü Phosphate-bonded high-alumina plastics with an alumina content between 70% and 90%, ü Phosphate-bonded chromium-alumina plastics, ü E-based phosphate-bonded plastics of silicon carbide. Ramming mixtures essentially composed of ground refractory aggregates, with a semi-plastic bond matrix appearance. These refractories are similar to plastic refractories but are much harder. They need some sort of shape to hold them once formed. The grain sizes are carefully classified and the final product is usually dried and then mixed with a little water immediately before use. Other tamping products are rendered in a wet state and are ready for use immediately after opening. The compacting mixtures are placed with a pneumatic rammer in layers of 25 mm to 40 mm. Steel production, burner blocks, doors and similar applications used of high purity tamping mixes based on mullite grain. Ramming mixes consist of 80wt. The % alumina content has good resistance to shrinkage and thermal spalling at high temperatures. Some compacting mixtures, such as high-alumina stabilized air, have good resistance to thermal spalling at high temperatures and volume stability up to the temperature limit. Additionally, phosphate-bonded alumina-chromium tamping mixes typically have very high resistance to high temperatures and excellent resistance to acids and neutral slags made from coal ash slag. Alumina-graphite tamping mixes contain a mixture of alumina granules and slag inhibitors which give them excellent resistance to acidic and slightly basic slags. In the steel industry, dry pressing mixtures based on high-purity MgO and a sintering aid are useful. Magnesite pressing mixes of exceptional purity and stability are used primarily as lining materials for crucible induction furnaces. Magnesia-Chromium fused grain tamping mixes can create special strength and density [52-60, 64-73]. The method of installing multiple monolithic refractories is injection. The spray mix material consists of particles of varying sizes of refractory aggregate, a binding compound, and may contain a plasticizing agent to improve tackiness when pneumatically placed on the furnace surface. These refractory materials are sprayed onto the application surfaces using a spray gun. Refractory spray mixes are usually supplied dry. For application, they are pre-moistened in a batch mixer and then continuously poured in.