Showing papers on "Hydrofluoric acid published in 2015"
01 Jan 2015
TL;DR: Fluoropolymer is a polymer consisting of carbon (C) and fluorine (F), sometimes referred to as perfluorpolymers to distinguish them from partially fluorinated polymers, fluoroelastomers, and other polymers that contain fluorine in their chemical structure.
Abstract: The reactivity of halogens decreases from top (fluorine) to bottom (Astatine) of the Group 17 in the Periodic Table of Elements. Substituting fluorine for any element such as hydrogen in the chemical structure of a compound will have a profound impact on its properties because fluorine is the most reactive of all elements. Slight fluorination renders the neutral surface of a polyolefin film polar. Further increases in the fluorine content results in total neutrality of the film surface. To reduce its reactivity and hazard, fluorine is diluted with nitrogen; a 10% F 2 in nitrogen can be stored and transported in passivated steel bottles. Fluoropolymer is a polymer consisting of carbon (C) and fluorine (F), sometimes these are referred to as perfluoropolymers to distinguish them from partially fluorinated polymers, fluoroelastomers, and other polymers that contain fluorine in their chemical structure. The basic properties of fluoropolymers arise from the atomic structure of fluorine and carbon and their covalent bonding in specific chemical structures. These properties are weakened as the chemical structure becomes less “perfluorinated”, as in polyvinylidene fluoride. They also offer thermal stability for use at high temperatures because they do not react with process streams; they help prevent contamination of products.
213 citations
TL;DR: In this paper, UiO-66 with crystal size ranging from hundreds of nanometers to a few micrometers and with cubic and cuboctahedral morphologies were synthesized.
Abstract: UiO-66 with crystal size ranging from hundreds of nanometers to a few micrometers and with cubic and cuboctahedral morphologies were synthesized. Crystal size and morphology varied with the additive amount of hydrofluoric acid and the concentration of reactants (ZrCl4 and H2BDC) during solvothermal synthesis. According to energy dispersive spectrometry (EDS) and 19F MAS NMR measurements, the fluorine ions directly bonded to Zr in the SBUs (secondary building units) in the MOF framework due to their strongest electronegativity. The bonding of the fluorine ions and Zr not only compensated for the charge imbalance of the framework caused by missing linkers but also competed with the linkers to coordinate with the Zr metal centers, thereby controlling the processes of nucleation and growth of the UiO-66 crystals. The samples were further characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA) and Ar sorption isotherms, showing that the introduction of fluorine enhanced the thermostability and porosity of UiO-66.
164 citations
TL;DR: In this article, an active Sn-BEA catalyst can be directly synthesized in a non-fluoride medium via a dry gel conversion method with the aid of seed crystals.
90 citations
TL;DR: The HF concentration and UR influenced the bond strength and surface/interface morphology and μ-shear bond strength between IPS Empress Esthetic and IPS e.max Press ceramics and resin cement.
Abstract: Clinical Relevance The current results support that 7.5% and 10% concentrations of hydrofluoric acid are more reliable for etching glass ceramics than are higher or lower concentrations. The use of unfilled resin after silane resulted in higher microshear bond strength and provided better interaction between ceramic and resin cement.
78 citations
TL;DR: In this article, the surface of activated carbon fibers (ACFs) was modified by liquid oxidation using hydrofluoric acid to enhance the adsorption of CO2 by the fibers based on the effects of the oxygen-containing functional groups introduced on the surface.
52 citations
TL;DR: In this article, a pressure acid leaching was used to extract niobium and tantalum from a ferrocolumbite ore. The results showed that the maximum extraction of Nb and Ta, 90 and 80% respectively, was achieved at an HF concentration of 9% v/v, reaction temperature of 220°C, particle size of −45μm, solid-to-liquid ratio of 1.82% w/v.
38 citations
TL;DR: In this paper, a new process was developed to deposit magnesium fluoride (MgF2) thin films via atomic layer deposition (ALD) for use as optical coatings in the ultraviolet.
Abstract: A new process has been developed to deposit magnesium fluoride (MgF2) thin films via atomic layer deposition (ALD) for use as optical coatings in the ultraviolet. MgF2 was deposited in a showerhead style ALD reactor using bis(ethylcyclopentadienyl)magnesium and anhydrous hydrogen fluoride (HF) as precursors at substrate temperatures from 100 to 250 °C. The use of HF was observed to result in improved morphology and reduced impurity content compared to other reported MgF2 ALD approaches that use metal fluoride precursors as the fluorine-containing chemistry. Characterization of these films has been performed using spectroscopic ellipsometry, atomic force microscopy, and x-ray photoelectron spectroscopy for material deposited on silicon substrates. Films at all substrate temperatures were transparent at wavelengths down to 190 nm and the low deposition temperature combined with low surface roughness makes these coatings good candidates for a variety of optical applications in the far ultraviolet.
35 citations
TL;DR: In this article, a new kind of heat insulating films were prepared from dispersion of Cs0.33WO3−xFx nanoparticles in polyvinyl alcohol (PVA) aqueous solution.
33 citations
TL;DR: In this paper, the incorporation of various types of chemical additives has been investigated, these in combination with hydrofluoric acid electrolyte and high-resistivity p-type parent substrates.
27 citations
TL;DR: In this article, a methanol-to-propylene (MTP) catalyst was designed both at the molecular scale, exhibiting low Bronsted acid site density, and at the microscopic level since large crystals (25 μm) with few defects were obtained.
26 citations
TL;DR: White fluorinated graphene oxide was obtained from graphene oxide under hydrothermal conditions with the coexistence of nitric and hydrofluoric acid, and characterized with an atomic percentage of 21.5 for oxygen and 14.2 for fluorine, thus ensuring good dispersibility in water.
Abstract: White fluorinated graphene oxide was obtained from graphene oxide under hydrothermal conditions with the coexistence of nitric and hydrofluoric acid, and characterized with an atomic percentage of 21.5 for oxygen and 14.2 for fluorine, thus ensuring good dispersibility in water.
TL;DR: In this article, the effect of 2.5% Cu addition on the corrosion resistance of Ni-30Co-16Cr-15Mo-6Fe alloy in hydrofluoric acid was investigated by immersion testing at 100°C.
TL;DR: The results obtained show that the anions have a stronger effect with respect to cations in their capacity for interacting with hydrofluoric acid, and the strongest interaction energies occur in systems where the key noncovalent interactions are mainly hydrogen bonds.
Abstract: In this work, we evaluated the energetic interactions between imidazolium ionic liquids (ILs) and hydrofluoric acid, as well as the cation–anion interactions in ILs. We used DFT calculations that include dispersion corrections employing the PBE and M06 functionals. We tested 22 ILs, including [C4MIM][PF6], [C4MIM][NTf2], and [C4MIM][CH3COO], obtaining interaction energies in the range of −27 to −13 kcal/mol with the PBE functional. The NCI (noncovalent interaction) index developed by Yang and collaborators (J. Am. Chem. Soc. 2010, 132, 6498−6506; J. Chem. Theory Comput. 2011, 7, 625–632) also was used for mapping the key noncovalent interactions (hydrogen bonds, van der Waals, and steric repulsions) between the anions and cations of ILs and also for interactions of ILs with hydrofluoric acid (HF). The results obtained show that the anions have a stronger effect with respect to cations in their capacity for interacting with hydrofluoric acid, and the strongest interaction energies occur in systems where th...
TL;DR: In this paper, a methanol-to-propylene catalyst was designed both at the molecular scale, exhibiting low Bronsted acid site density, and at the microscopic level providing large crystals (25 µm) with few defects.
Abstract: A promising methanol-to-propylene catalyst was designed both at the molecular scale, exhibiting low Bronsted acid site density, and at the microscopic level providing large crystals (25 µm) with few defects. The potential of giant ZSM-5 zeolites synthesized in fluoride medium in the conversion of methanol into propylene led us to investigate the replacement of harmful hydrofluoric acid by non-toxic H3PO4. P-ZSM-5 zeolites were synthesized and thoroughly characterized by XRD, SEM, FT-IR, TPD propylamine, H/D isotope exchange and XRF analyses. The catalytic performance of these acid catalysts was evaluated in the methanol-to-olefins reaction at 673 K. The presence of phosphorous in the zeolite after calcination was ascertained and induced high ethylene selectivity (up to 33 %) and improved catalyst stability with respect to fluoride-mediated zeolites.
TL;DR: In this article, the porosity has little influence on the corrosion resistance of the sintered porous Ni-Cu alloy in hydrofluoric acid solution, which is most likely due to the homogenous pore structure and chemical composition of the material, as well as the chemical stability of the bulk alloy.
TL;DR: A room temperature refining process using a new acidic mixture was investigated for the purification of metallurgical grade-silicon (MG-Si) with an average particle size of 617μm.
Patent•
IBM1
TL;DR: In this paper, a method that allows effective removal of a silicon-containing antireflective coating (SiARC) layer in a block mask after defining an unblock area in a sidewall image transfer (SIT) patterning process without causing a height loss of the SIT spacers is provided.
Abstract: A method that allows effective removal of a silicon-containing antireflective coating (SiARC) layer in a block mask after defining an unblock area in a sidewall image transfer (SIT) patterning process without causing a height loss of the SIT spacers is provided. The method includes first modifying the SiARC layer with a dry etch utilizing an etching gas comprising a nitrogen gas followed by treating the modified SiARC layer with a wet chemical etch utilizing an aqueous solution including dilute hydrofluoric acid and citric acid.
Patent•
16 Dec 2015
TL;DR: In this article, the authors provided a polycrystalline black silicon texturization treatment fluid, which consisted of a hydrofluoric acid solution, a hydrogen peroxide solution and a metal salt.
Abstract: The invention provides a polycrystalline black silicon texturization treatment fluid. The polycrystalline black silicon texturization treatment fluid comprises a hydrofluoric acid solution, a hydrogen peroxide solution and a metal salt, wherein a volume ratio of the hydrofluoric acid solution to the hydrogen peroxide solution is 1-25:5-40, the mass fraction of hydrofluoric acid in the hydrofluoric acid solution is 40-50%, the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 20-55%, the metal salt is at least one of copper nitrate, silver nitrate, palladium nitrate, copper chloride, auric chloride acid, chloroplatinic acid, potassium chromate and nickel sulfate, and the mole concentration of the metal salt is 1-10 [mu]mol/L. The invention also provides a polysilicon chip texturization method applying the polycrystalline black silicon texturization treatment fluid, and a polycrystalline black silicon texturization product.
TL;DR: The HNO3-free mixtures might allow to replace KOH/i-propanol and similar alkaline solutions for texturization of monosilicon wafers at room temperature with less surface contamination with significant economic and ecological advantages.
Abstract: The wet-chemical treatment of silicon wafers is an important production step in photovoltaic and semiconductor industries. Solutions containing hydrofluoric acid, ammonium peroxodisulfate, and hydrochloric acid were investigated as novel acidic, NOx-free etching mixtures for texturization and polishing of monocrystalline silicon wafers. Etching rates as well as generated surface morphologies and properties are discussed in terms of the composition of the etching mixture. The solutions were analyzed with Raman and UV/vis spectroscopy as well as ion chromatography (IC). The silicon surfaces were investigated by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), diffuse reflection infrared spectroscopy (DRIFT), and X-ray photoelectron spectroscopy (XPS). Surprisingly, pyramidal surface structures were found after etching SiC-slurry as well as diamond wire-sawn monocrystalline Si(100) wafers with hydrochloric acid-rich HF-(NH4)2S2O8-HCl mixtures. Acidic etching solutions are generally not known for anisotropic etching. Thus, the HNO3-free mixtures might allow to replace KOH/i-propanol and similar alkaline solutions for texturization of monosilicon wafers at room temperature with less surface contamination. Besides, common HNO3-based etching mixtures may be replaced by the nitrate-free system, leading to significant economic and ecological advantages.
Patent•
25 Nov 2015
TL;DR: In this paper, a shale gas reservoir pre-fracture composite acid solution and its preparation method and application is discussed, which consists of the following components: Component a) at least one component of hydrochloric acid, hydrofluoric acid, fluorboric acid and formic acid; component b) a corrosion inhibitor, a discharge aiding agent, a ferric iron stabilizer and a clay stabilizer.
Abstract: The invention belongs to the field of petroleum engineering and relates to a shale gas reservoir pre-fracture composite acid solution and its preparation method and application. The composite acid solution comprises the following components: Component a) at least one component of hydrochloric acid, hydrofluoric acid, fluorboric acid, phosphoric acid, formic acid and acetic acid; and Component b) a corrosion inhibitor, a discharge aiding agent, a ferric iron stabilizer and a clay stabilizer. The composite acid solution containing different acids is selected for different reservoirs. Rock core corrosion ratio is 25-30%. A certain rock core corrosion ratio is maintained, and borehole wall collapse caused by too high corrosion ratio is also prevented. The corrosion inhibitor, the discharge aiding agent, the ferric iron stabilizer and the clay stabilizer which are used as additives have good compatibility with acid. The composite acid solution provided by the invention has advantages of fast dissolving speed, uniform mixing, high corrosion inhibition efficiency, high surface activity, good clay stabilizing effect and wide range. Applicable temperature of the composite acid solution is 20-180 DEG C. by the use of the composite acid solution, normal construction of large-scale fracturing of long horizontal-section shale gas wells can be guaranteed under the condition of existing equipment capacity.
TL;DR: The effect of using different electrolytes in the physical and optical properties of porous silicon was studied in this article, where two electrolytes were used: a mixture of hydrofluoric acid (HF), ethanol (CH3-CH2-OH), and hydrogen peroxide (H2O2) in a ratio of 1 : 1 : 2.
Abstract: The effect of using different electrolytes in the physical and optical properties of porous silicon was studied. To do this porous silicon (PS) samples photoluminescent in the visible range from (100) oriented n-type crystalline silicon prepared by anodic etching were obtained. The first electrolyte was composed of a mixture of hydrofluoric acid (HF) and ethanol (CH3-CH2-OH) in a ratio of 1 : 2, respectively. The second was composed of hydrofluoric acid (HF), ethanol (CH3-CH2-OH), and hydrogen peroxide (H2O2) in a ratio of 1 : 1 : 2, respectively. Raman scattering, photoluminescence (PL), gravimetry, scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS) measurements on the PSL were carried out. Raman scattering showed that the disorder in the samples obtained with H2O2 is greater than in the samples obtained without this. The PL from PS increased in intensity with the incremental change in the anodization time and showed a blueshift. The blueshift of PL is consistent with the reduction in size of the silicon nanocrystallites. The sizes of nanocrystals were estimated to be 3.08, 2.6, and 2.28 nm. The gravimetric analysis showed that the porosity increased with the incorporation of H2O2. SEM images (morphological analysis) showed an incremental change in the quantity and in the porous size.
TL;DR: In this article, the quantum-chemical simulation of the interaction of F− and FHF− ions with the single-crystal graphene and grain-boundary-containing graphene surface is represented.
Patent•
11 Nov 2015
TL;DR: In this article, a method for surface modification of the Mn doped fluoride fluorescent powder particles was proposed, where the surfaces of the prepared A2[MF6] particles were coated with an inorganic or organic functional material through a monoatomic deposition technology, a chemical precipitation reaction method and a surface chemical coating modification method.
Abstract: The invention relates to a preparation method of a Mn doped fluoride fluorescent powder material and a method for the surface modification of the Mn doped fluoride fluorescent powder material, and belongs to the field of preparation of LED fluorescent powder. The preparation method comprises the following steps: firstly, preparing A2MnF6; then, dropwise adding a second solution, obtained through dissolving fluoride or hydrofluoride of A into a hydrofluoric acid solution, into a first solution containing an HF solution, A2MnF6 and fluoride of a quadrivalent element M, and performing solid-liquid separation, so as to obtain a solid precipitation product generated after reaction. The fluorescent powder prepared by the method is small in particle size and excellent in luminous performance. The invention further provides a method for the surface modification of the Mn doped fluoride fluorescent powder particles. The surfaces of the prepared A2[MF6]:Mn fluoride red fluorescent powder particles are coated with an inorganic or organic functional material through a monoatomic deposition technology, a chemical precipitation reaction method and a surface chemical coating modification method, so that the stability of the prepared A2[MF6]:Mn fluoride red fluorescent powder particles in high-temperature and high-humidity environments is remarkably improved.
TL;DR: In this paper, a triglycine sulfate structure with cations of the "triglycinear sulfate" type without a doubly charged counter-ion was presented.
Abstract: L-Cysteine hydrogen fluoride, or bis(L-cysteinium) difluoride-L-cysteine-hydrogen fluoride (1/1/1), 2C3H8NO2S(+)·2F(-)·C3H7NO2S·HF or L-Cys(+)(L-Cys···L-Cys(+))F(-)(F(-)...H-F), provides the first example of a structure with cations of the 'triglycine sulfate' type, i.e. A(+)(A···A(+)) (where A and A(+) are the zwitterionic and cationic states of an amino acid, respectively), without a doubly charged counter-ion. The salt crystallizes in the monoclinic system with the space group P2(1). The dimeric (L-Cys···L-Cys(+)) cation and the dimeric (F(-)···H-F) anion are formed via strong O-H···O or F-H···F hydrogen bonds, respectively, with very short O···O [2.4438 (19) A] and F···F distances [2.2676 (17) A]. The F···F distance is significantly shorter than in solid hydrogen fluoride. Additionally, there is another very short hydrogen bond, of O-H···F type, formed by a L-cysteinium cation and a fluoride ion. The corresponding O···F distance of 2.3412 (19) A seems to be the shortest among O-H···F and F-H···O hydrogen bonds known to date. The single-crystal X-ray diffraction study was complemented by IR spectroscopy. Of special interest was the spectral region of vibrations related to the above-mentioned hydrogen bonds.
TL;DR: This novel material, displaying a nanoscopic lamellar structure, has been synthesized at the surface of an aqueous solution of LaCl3 and HF and is highly promising for many typical applications of fluorine ionic systems.
Abstract: Ionically conducting lanthanum fluoride (LaF3), displaying a nanoscopic lamellar structure, has been synthesized at the surface of an aqueous solution of LaCl3 and HF. The structure and the chemical composition of the conductor have been analyzed by SEM, electron probe microanalysis, X-ray powder diffraction, FTIR, and (19)F magic angle spinning nuclear magnetic resonance (NMR) spectroscopy. The fluorine dynamics have been studied by NMR diffusometry and relaxometry in a temperature range from room temperature up to 875 K. The fluorine self-diffusion coefficient of the nanostructured LaF3 is about two orders of magnitude larger than that of bulk LaF3. This novel material is highly promising for many typical applications of fluorine ionic systems.
Patent•
15 Jan 2015TL;DR: In this article, a method for producing a red phosphor which is a Mn-activated complex fluoride represented by formula (1),676A 2 MF 6 : Mn (1)¯¯¯¯(M is one type or more of a tetravalent element selected from Si, Ti, Zr, Hf, Ge, and Sn, and A is either an alkali metal selected from Li, Na, K, Rb, and Cs, and includes at least Na and/or K).
Abstract: Provided is a method for producing a red phosphor which is a Mn-activated complex fluoride represented by formula (1),
A 2 MF 6 : Mn (1)
(M is one type or more of a tetravalent element selected from Si, Ti, Zr, Hf, Ge, and Sn, and A is one type or more of an alkali metal selected from Li, Na, K, Rb, and Cs, and includes at least Na and/or K.), wherein, as a reactive source, a solid of a complex fluoride represented by formula (2),
A 2 MF 6 (2)
(M and A are as described above) and a solid of a manganese compound represented by formula (3),
A 2 MnF 6 (3)
(A is as described above) are mixed and heated at a temperature of from 100°C to 500°C. According to the present invention, a Mn-activated complex fluoride phosphor having favorable luminescence properties can be obtained without using hydrofluoric acid in a main step.
TL;DR: In this article, the effect of HF and HNO3 concentrations on etching rates of several components such as silver (Ag), aluminum (Al), anti-reflection film made of silicon nitride (AR) and silicon (Si) in the solar cells has been made clear.
Abstract: In order to maximize the recovery of silicon wafer in waste crystalline silicon solar cells, chemical treatment has been carried out by using the mixed solution of hydrofluoric acid (HF) and nitric acid (HNO3). The effect of HF and HNO3 concentrations on etching rates of several components such as silver (Ag), aluminum (Al), anti-reflection film made of silicon nitride (AR) and silicon (Si) in the solar cells has been made clear. The etching rates of Ag, Al and Si are held almost constant with time and become larger with the increasing HF concentration and the etching temperature. All of the etching rates of Al, AR and Si have peaked at the HF mole fraction of about 0.8. The dependency of HF concentration on Al, AR and Si etching rates becomes larger than that of HNO3. As the best solution composition for the Si recovery yield, the following relation has been found in this study: (number of AR moles)/(number of Al moles) = 7.62 © 1014 CHNO3CHF where CHNO3, CHF: HNO3, HF concentration (kmol/m3). [doi:10.2320/matertrans.M2015293]
Patent•
25 Mar 2015
TL;DR: In this paper, a method for joint measurement of calcium-barium content of a silicon barium alloy by using compleximetry is described, and the method is characterized by comprising the following steps: dissolving a sample by using nitric acid and hydrofluoric acid; adding perchloric acid until smoke is generated; steaming until the sample is dried; dissolving salts by using hydro chloric acid, fixing volume by using water, then taking two samples, and adding a masking agent into the two samples respectively to eliminate interference elements; then mixing calcein
Abstract: The invention relates to a method for joint measurement of calcium-barium content of a silicon-barium alloy by using compleximetry. The method is characterized by comprising the following steps: dissolving a sample by using nitric acid and hydrofluoric acid; adding perchloric acid until smoke is generated; steaming until the sample is dried; dissolving salts by using hydrochloric acid, fixing volume by using water, then taking two samples, and adding a masking agent into the two samples respectively to eliminate interference elements; then mixing calcein with an indicator; performing titration by using EDTA (ethylene diamine tetraacetic acid) as a standard solution to measure the calcium-barium content and the calcium content respectively; and performing subtractive calculation to obtain the barium content. The method has the following advantages: by virtue of joint measurement, simultaneous measurements by one time of sample dissolving are realized, and successive measurements by two times of sample dissolving are not needed, so that the operation time is greatly shortened, and the operation is quick and accurate; by one time of sample dissolving, the labor capacity of workers is reduced, the added types and added amount of chemicals are greatly reduced, the cost is saved, the use frequency of a electric hot plate is reduced, and the energy consumption is reduced.
TL;DR: In this article, a comparison of electrochemical cycling of atomic-layer-deposited TiO2 anodes using LiPF6 with and without a hydrofluoric acid scavenger, tributylamine, to cycling using a nonfluorinated lithium perchlorate (LiClO4) salt indicates that the in situ formation of hydro-fluororic acid in the electrolyte from decomposition of the PF6-anion alters cycling stability.
Abstract: Titanium dioxide has been identified as a prospective anode material for use in lithium ion batteries. The higher lithiation potential of TiO2 versus other common anodes is more electrochemically compatible with most organic electrolytes, thus leading to reduced solid electrolyte interphase formation and overall more stable battery systems. However, in this study TiO2 has exhibited poor cycling stability with common electrolytes containing lithium hexafluorophosphate (LiPF6) salt. Combined electrochemical and spectroscopic analyses have revealed this to be due to the onset of reversible fluorination of the anode and chemical conversion of TiO2 to TiOF2 during lithiation. Comparison of electrochemical cycling of atomic-layer-deposited TiO2 anodes using LiPF6 with and without a hydrofluoric acid scavenger, tributylamine, to cycling using a nonfluorinated lithium perchlorate (LiClO4) salt indicates that the in situ formation of hydrofluoric acid in the electrolyte from decomposition of the PF6– anion alters ...
02 Apr 2015
TL;DR: In this article, the results of laboratory investigations of different acid combinations (HF: HCl, HF: H3PO4 and HF: HCOOH) were presented, and it was found that the buffer effect of PHO and formic acid is better than hydrochloric acid.
Abstract: The most important concern of sandstone matrix acidizing is to increase the formation permeability by removing the silica particles. To accomplish this, the mud acid (HF: HCl) has been utilized successfully for many years to stimulate the sandstone formations, but still it has many complexities. This paper presents the results of laboratory investigations of different acid combinations (HF: HCl, HF: H3PO4 and HF: HCOOH). Hydrofluoric acid and fluoboric acid are used to dissolve clays and feldspar. Phosphoric and formic acids are added as a buffer to maintain the pH of the solution; also it allows the maximum penetration of acid into the core sample. Different tests have been performed on the core samples before and after the acidizing to do the comparative study on the buffer effect of these acids. The analysis consists of permeability, porosity, color change and pH value tests. There is more increase in permeability and porosity while less change in pH when phosphoric and formic acids were used compared to mud acid. From these results it has been found that the buffer effect of phosphoric acid and formic acid is better than hydrochloric acid.